diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1e3098c..4d17af8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -135,7 +135,7 @@
         set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wlogical-op")
     endif()
     if (GCC_VERSION VERSION_GREATER 4.8 OR GCC_VERSION VERSION_EQUAL 4.8)
-        set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wshadow")
+        set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wshadow -Wformat-signedness")
     endif()
     set(CMAKE_C_FLAGS_RELEASE     "-O2")
     set(CMAKE_C_FLAGS_DEBUG       "-O0 -g3")
diff --git a/ChangeLog.d/fix-gcc-format-signedness-warnings.txt b/ChangeLog.d/fix-gcc-format-signedness-warnings.txt
new file mode 100644
index 0000000..023d15c
--- /dev/null
+++ b/ChangeLog.d/fix-gcc-format-signedness-warnings.txt
@@ -0,0 +1,3 @@
+Changes
+   * Fix warnings about signedness issues in format strings. The build is now
+     clean of -Wformat-signedness warnings. Contributed by Kenneth Soerensen in #3153.
diff --git a/library/aes.c b/library/aes.c
index 604d0f3..962b0b9 100644
--- a/library/aes.c
+++ b/library/aes.c
@@ -1847,7 +1847,7 @@
         mode = i & 1;
 
         if( verbose != 0 )
-            mbedtls_printf( "  AES-ECB-%3d (%s): ", keybits,
+            mbedtls_printf( "  AES-ECB-%3u (%s): ", keybits,
                             ( mode == MBEDTLS_AES_DECRYPT ) ? "dec" : "enc" );
 
         memset( buf, 0, 16 );
@@ -1909,7 +1909,7 @@
         mode = i & 1;
 
         if( verbose != 0 )
-            mbedtls_printf( "  AES-CBC-%3d (%s): ", keybits,
+            mbedtls_printf( "  AES-CBC-%3u (%s): ", keybits,
                             ( mode == MBEDTLS_AES_DECRYPT ) ? "dec" : "enc" );
 
         memset( iv , 0, 16 );
@@ -1984,7 +1984,7 @@
         mode = i & 1;
 
         if( verbose != 0 )
-            mbedtls_printf( "  AES-CFB128-%3d (%s): ", keybits,
+            mbedtls_printf( "  AES-CFB128-%3u (%s): ", keybits,
                             ( mode == MBEDTLS_AES_DECRYPT ) ? "dec" : "enc" );
 
         memcpy( iv,  aes_test_cfb128_iv, 16 );
@@ -2047,7 +2047,7 @@
         mode = i & 1;
 
         if( verbose != 0 )
-            mbedtls_printf( "  AES-OFB-%3d (%s): ", keybits,
+            mbedtls_printf( "  AES-OFB-%3u (%s): ", keybits,
                             ( mode == MBEDTLS_AES_DECRYPT ) ? "dec" : "enc" );
 
         memcpy( iv,  aes_test_ofb_iv, 16 );
diff --git a/library/bignum.c b/library/bignum.c
index d53aefd..d56a16e 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -2938,7 +2938,7 @@
 cleanup:
 
     if( ret != 0 && verbose != 0 )
-        mbedtls_printf( "Unexpected error, return code = %08X\n", ret );
+        mbedtls_printf( "Unexpected error, return code = %08X\n", (unsigned int) ret );
 
     mbedtls_mpi_free( &A ); mbedtls_mpi_free( &E ); mbedtls_mpi_free( &N ); mbedtls_mpi_free( &X );
     mbedtls_mpi_free( &Y ); mbedtls_mpi_free( &U ); mbedtls_mpi_free( &V );
diff --git a/library/cmac.c b/library/cmac.c
index 642680d..2d23be5 100644
--- a/library/cmac.c
+++ b/library/cmac.c
@@ -784,7 +784,7 @@
     for( i = 0; i < num_tests; i++ )
     {
         if( verbose != 0 )
-            mbedtls_printf( "  %s CMAC subkey #%u: ", testname, i + 1 );
+            mbedtls_printf( "  %s CMAC subkey #%d: ", testname, i + 1 );
 
         mbedtls_cipher_init( &ctx );
 
@@ -865,7 +865,7 @@
     for( i = 0; i < num_tests; i++ )
     {
         if( verbose != 0 )
-            mbedtls_printf( "  %s CMAC #%u: ", testname, i + 1 );
+            mbedtls_printf( "  %s CMAC #%d: ", testname, i + 1 );
 
         if( ( ret = mbedtls_cipher_cmac( cipher_info, key, keybits, messages,
                                          message_lengths[i], output ) ) != 0 )
@@ -900,7 +900,7 @@
 
     for( i = 0; i < NB_PRF_TESTS; i++ )
     {
-        mbedtls_printf( "  AES CMAC 128 PRF #%u: ", i );
+        mbedtls_printf( "  AES CMAC 128 PRF #%d: ", i );
         ret = mbedtls_aes_cmac_prf_128( PRFK, PRFKlen[i], PRFM, 20, output );
         if( ret != 0 ||
             memcmp( output, PRFT[i], MBEDTLS_AES_BLOCK_SIZE ) != 0 )
diff --git a/library/debug.c b/library/debug.c
index ae78a69..2b25e99 100644
--- a/library/debug.c
+++ b/library/debug.c
@@ -132,7 +132,7 @@
         return;
 
     mbedtls_snprintf( str, sizeof( str ), "%s() returned %d (-0x%04x)\n",
-              text, ret, -ret );
+              text, ret, (unsigned int) -ret );
 
     debug_send_line( ssl, level, file, line, str );
 }
diff --git a/library/ecp.c b/library/ecp.c
index d3e42a9..fa91b3e 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -3156,7 +3156,7 @@
 cleanup:
 
     if( ret < 0 && verbose != 0 )
-        mbedtls_printf( "Unexpected error, return code = %08X\n", ret );
+        mbedtls_printf( "Unexpected error, return code = %08X\n", (unsigned int) ret );
 
     mbedtls_ecp_group_free( &grp );
     mbedtls_ecp_point_free( &R );
diff --git a/library/error.c b/library/error.c
index 38b6580..d2f1b18 100644
--- a/library/error.c
+++ b/library/error.c
@@ -1171,7 +1171,7 @@
         high_level_error_description = mbedtls_high_level_strerr( ret );
 
         if( high_level_error_description == NULL )
-            mbedtls_snprintf( buf, buflen, "UNKNOWN ERROR CODE (%04X)", use_ret );
+            mbedtls_snprintf( buf, buflen, "UNKNOWN ERROR CODE (%04X)", (unsigned int) use_ret );
         else
             mbedtls_snprintf( buf, buflen, "%s", high_level_error_description );
 
@@ -1208,7 +1208,7 @@
     low_level_error_description = mbedtls_low_level_strerr( ret );
 
     if( low_level_error_description == NULL )
-        mbedtls_snprintf( buf, buflen, "UNKNOWN ERROR CODE (%04X)", use_ret );
+        mbedtls_snprintf( buf, buflen, "UNKNOWN ERROR CODE (%04X)", (unsigned int) use_ret );
     else
         mbedtls_snprintf( buf, buflen, "%s", low_level_error_description );
 }
diff --git a/library/oid.c b/library/oid.c
index 891d3cd..e0c0743 100644
--- a/library/oid.c
+++ b/library/oid.c
@@ -761,7 +761,7 @@
         if( !( oid->p[i] & 0x80 ) )
         {
             /* Last byte */
-            ret = mbedtls_snprintf( p, n, ".%d", value );
+            ret = mbedtls_snprintf( p, n, ".%u", value );
             OID_SAFE_SNPRINTF;
             value = 0;
         }
diff --git a/library/x509.c b/library/x509.c
index c451332..4c2f721 100644
--- a/library/x509.c
+++ b/library/x509.c
@@ -870,7 +870,7 @@
         ret = mbedtls_snprintf( p, n, " (%s, MGF1-%s, 0x%02X)",
                               md_info ? mbedtls_md_get_name( md_info ) : "???",
                               mgf_md_info ? mbedtls_md_get_name( mgf_md_info ) : "???",
-                              pss_opts->expected_salt_len );
+                              (unsigned int) pss_opts->expected_salt_len );
         MBEDTLS_X509_SAFE_SNPRINTF;
     }
 #else
diff --git a/programs/aes/aescrypt2.c b/programs/aes/aescrypt2.c
index 048028d..8edf85f 100644
--- a/programs/aes/aescrypt2.c
+++ b/programs/aes/aescrypt2.c
@@ -118,7 +118,7 @@
     ret = mbedtls_md_setup( &sha_ctx, mbedtls_md_info_from_type( MBEDTLS_MD_SHA256 ), 1 );
     if( ret != 0 )
     {
-        mbedtls_printf( "  ! mbedtls_md_setup() returned -0x%04x\n", -ret );
+        mbedtls_printf( "  ! mbedtls_md_setup() returned -0x%04x\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -298,7 +298,7 @@
 
             if( fread( buffer, 1, n, fin ) != (size_t) n )
             {
-                mbedtls_fprintf( stderr, "fread(%d bytes) failed\n", n );
+                mbedtls_fprintf( stderr, "fread(%u bytes) failed\n", n );
                 goto exit;
             }
 
@@ -413,7 +413,7 @@
 
             if( fwrite( buffer, 1, n, fout ) != (size_t) n )
             {
-                mbedtls_fprintf( stderr, "fwrite(%d bytes) failed\n", n );
+                mbedtls_fprintf( stderr, "fwrite(%u bytes) failed\n", n );
                 goto exit;
             }
         }
diff --git a/programs/aes/crypt_and_hash.c b/programs/aes/crypt_and_hash.c
index a5acf5b..e2949f2 100644
--- a/programs/aes/crypt_and_hash.c
+++ b/programs/aes/crypt_and_hash.c
@@ -219,7 +219,7 @@
             p = &argv[6][4];
             keylen = 0;
 
-            while( sscanf( p, "%02X", &n ) > 0 &&
+            while( sscanf( p, "%02X", (unsigned int*) &n ) > 0 &&
                    keylen < (int) sizeof( key ) )
             {
                 key[keylen++] = (unsigned char) n;
@@ -417,7 +417,7 @@
             ( ( filesize - mbedtls_md_get_size( md_info ) ) %
                 mbedtls_cipher_get_block_size( &cipher_ctx ) ) != 0 )
         {
-            mbedtls_fprintf( stderr, "File content not a multiple of the block size (%d).\n",
+            mbedtls_fprintf( stderr, "File content not a multiple of the block size (%u).\n",
                      mbedtls_cipher_get_block_size( &cipher_ctx ));
             goto exit;
         }
@@ -484,7 +484,7 @@
 
             if( fread( buffer, 1, ilen, fin ) != ilen )
             {
-                mbedtls_fprintf( stderr, "fread(%d bytes) failed\n",
+                mbedtls_fprintf( stderr, "fread(%u bytes) failed\n",
                     mbedtls_cipher_get_block_size( &cipher_ctx ) );
                 goto exit;
             }
diff --git a/programs/pkey/gen_key.c b/programs/pkey/gen_key.c
index 23e4e14..9c1a91c 100644
--- a/programs/pkey/gen_key.c
+++ b/programs/pkey/gen_key.c
@@ -302,7 +302,7 @@
                                         NULL, DEV_RANDOM_THRESHOLD,
                                         MBEDTLS_ENTROPY_SOURCE_STRONG ) ) != 0 )
         {
-            mbedtls_printf( " failed\n  ! mbedtls_entropy_add_source returned -0x%04x\n", -ret );
+            mbedtls_printf( " failed\n  ! mbedtls_entropy_add_source returned -0x%04x\n", (unsigned int) -ret );
             goto exit;
         }
 
@@ -315,7 +315,7 @@
                                (const unsigned char *) pers,
                                strlen( pers ) ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%04x\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%04x\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -328,7 +328,7 @@
     if( ( ret = mbedtls_pk_setup( &key,
             mbedtls_pk_info_from_type( (mbedtls_pk_type_t) opt.type ) ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  !  mbedtls_pk_setup returned -0x%04x", -ret );
+        mbedtls_printf( " failed\n  !  mbedtls_pk_setup returned -0x%04x", (unsigned int) -ret );
         goto exit;
     }
 
@@ -339,7 +339,7 @@
                                    opt.rsa_keysize, 65537 );
         if( ret != 0 )
         {
-            mbedtls_printf( " failed\n  !  mbedtls_rsa_gen_key returned -0x%04x", -ret );
+            mbedtls_printf( " failed\n  !  mbedtls_rsa_gen_key returned -0x%04x", (unsigned int) -ret );
             goto exit;
         }
     }
@@ -353,7 +353,7 @@
                                    mbedtls_ctr_drbg_random, &ctr_drbg );
         if( ret != 0 )
         {
-            mbedtls_printf( " failed\n  !  mbedtls_ecp_gen_key returned -0x%04x", -ret );
+            mbedtls_printf( " failed\n  !  mbedtls_ecp_gen_key returned -0x%04x", (unsigned int) -ret );
             goto exit;
         }
     }
diff --git a/programs/pkey/key_app.c b/programs/pkey/key_app.c
index 19dcdfe..345b7b8 100644
--- a/programs/pkey/key_app.c
+++ b/programs/pkey/key_app.c
@@ -187,7 +187,7 @@
 
         if( ret != 0 )
         {
-            mbedtls_printf( " failed\n  !  mbedtls_pk_parse_keyfile returned -0x%04x\n", -ret );
+            mbedtls_printf( " failed\n  !  mbedtls_pk_parse_keyfile returned -0x%04x\n", (unsigned int) -ret );
             goto cleanup;
         }
 
@@ -248,7 +248,7 @@
 
         if( ret != 0 )
         {
-            mbedtls_printf( " failed\n  !  mbedtls_pk_parse_public_keyfile returned -0x%04x\n", -ret );
+            mbedtls_printf( " failed\n  !  mbedtls_pk_parse_public_keyfile returned -0x%04x\n", (unsigned int) -ret );
             goto cleanup;
         }
 
diff --git a/programs/pkey/key_app_writer.c b/programs/pkey/key_app_writer.c
index 6096429..937fe90 100644
--- a/programs/pkey/key_app_writer.c
+++ b/programs/pkey/key_app_writer.c
@@ -299,7 +299,7 @@
         if( ret != 0 )
         {
             mbedtls_strerror( ret, (char *) buf, sizeof(buf) );
-            mbedtls_printf( " failed\n  !  mbedtls_pk_parse_keyfile returned -0x%04x - %s\n\n", -ret, buf );
+            mbedtls_printf( " failed\n  !  mbedtls_pk_parse_keyfile returned -0x%04x - %s\n\n", (unsigned int) -ret, buf );
             goto exit;
         }
 
@@ -360,7 +360,7 @@
         if( ret != 0 )
         {
             mbedtls_strerror( ret, (char *) buf, sizeof(buf) );
-            mbedtls_printf( " failed\n  !  mbedtls_pk_parse_public_key returned -0x%04x - %s\n\n", -ret, buf );
+            mbedtls_printf( " failed\n  !  mbedtls_pk_parse_public_key returned -0x%04x - %s\n\n", (unsigned int) -ret, buf );
             goto exit;
         }
 
diff --git a/programs/pkey/pk_decrypt.c b/programs/pkey/pk_decrypt.c
index bf42507..bccfde0 100644
--- a/programs/pkey/pk_decrypt.c
+++ b/programs/pkey/pk_decrypt.c
@@ -100,7 +100,7 @@
                                        strlen( pers ) ) ) != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%04x\n",
-                        -ret );
+                        (unsigned int) -ret );
         goto exit;
     }
 
@@ -109,7 +109,7 @@
 
     if( ( ret = mbedtls_pk_parse_keyfile( &pk, argv[1], "" ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_pk_parse_keyfile returned -0x%04x\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_pk_parse_keyfile returned -0x%04x\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -124,7 +124,7 @@
     }
 
     i = 0;
-    while( fscanf( f, "%02X", &c ) > 0 &&
+    while( fscanf( f, "%02X", (unsigned int*) &c ) > 0 &&
            i < (int) sizeof( buf ) )
     {
         buf[i++] = (unsigned char) c;
@@ -142,7 +142,7 @@
                             mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_pk_decrypt returned -0x%04x\n",
-                        -ret );
+                        (unsigned int) -ret );
         goto exit;
     }
 
diff --git a/programs/pkey/pk_encrypt.c b/programs/pkey/pk_encrypt.c
index a32b147..16cd3f0 100644
--- a/programs/pkey/pk_encrypt.c
+++ b/programs/pkey/pk_encrypt.c
@@ -98,7 +98,7 @@
                                        strlen( pers ) ) ) != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%04x\n",
-                        -ret );
+                        (unsigned int) -ret );
         goto exit;
     }
 
@@ -107,7 +107,7 @@
 
     if( ( ret = mbedtls_pk_parse_public_keyfile( &pk, argv[1] ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_pk_parse_public_keyfile returned -0x%04x\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_pk_parse_public_keyfile returned -0x%04x\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -130,7 +130,7 @@
                             mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_pk_encrypt returned -0x%04x\n",
-                        -ret );
+                        (unsigned int) -ret );
         goto exit;
     }
 
diff --git a/programs/pkey/pk_sign.c b/programs/pkey/pk_sign.c
index a354e5b..4e755c0 100644
--- a/programs/pkey/pk_sign.c
+++ b/programs/pkey/pk_sign.c
@@ -96,7 +96,7 @@
                                (const unsigned char *) pers,
                                strlen( pers ) ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%04x\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%04x\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -127,7 +127,7 @@
     if( ( ret = mbedtls_pk_sign( &pk, MBEDTLS_MD_SHA256, hash, 0, buf, &olen,
                          mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_pk_sign returned -0x%04x\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_pk_sign returned -0x%04x\n", (unsigned int) -ret );
         goto exit;
     }
 
diff --git a/programs/pkey/pk_verify.c b/programs/pkey/pk_verify.c
index 72caf71..2e08763 100644
--- a/programs/pkey/pk_verify.c
+++ b/programs/pkey/pk_verify.c
@@ -86,7 +86,7 @@
 
     if( ( ret = mbedtls_pk_parse_public_keyfile( &pk, argv[1] ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_pk_parse_public_keyfile returned -0x%04x\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_pk_parse_public_keyfile returned -0x%04x\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -123,7 +123,7 @@
     if( ( ret = mbedtls_pk_verify( &pk, MBEDTLS_MD_SHA256, hash, 0,
                            buf, i ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_pk_verify returned -0x%04x\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_pk_verify returned -0x%04x\n", (unsigned int) -ret );
         goto exit;
     }
 
diff --git a/programs/pkey/rsa_decrypt.c b/programs/pkey/rsa_decrypt.c
index ff71bd0..3327909 100644
--- a/programs/pkey/rsa_decrypt.c
+++ b/programs/pkey/rsa_decrypt.c
@@ -160,7 +160,7 @@
 
     i = 0;
 
-    while( fscanf( f, "%02X", &c ) > 0 &&
+    while( fscanf( f, "%02X", (unsigned int*) &c ) > 0 &&
            i < (int) sizeof( buf ) )
         buf[i++] = (unsigned char) c;
 
diff --git a/programs/pkey/rsa_sign.c b/programs/pkey/rsa_sign.c
index 9bcd7a6..78ab176 100644
--- a/programs/pkey/rsa_sign.c
+++ b/programs/pkey/rsa_sign.c
@@ -129,7 +129,7 @@
     fflush( stdout );
     if( ( ret = mbedtls_rsa_check_privkey( &rsa ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_rsa_check_privkey failed with -0x%0x\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_rsa_check_privkey failed with -0x%0x\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -151,7 +151,7 @@
     if( ( ret = mbedtls_rsa_pkcs1_sign( &rsa, NULL, NULL, MBEDTLS_RSA_PRIVATE, MBEDTLS_MD_SHA256,
                                 20, hash, buf ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_rsa_pkcs1_sign returned -0x%0x\n\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_rsa_pkcs1_sign returned -0x%0x\n\n", (unsigned int) -ret );
         goto exit;
     }
 
diff --git a/programs/pkey/rsa_verify.c b/programs/pkey/rsa_verify.c
index 94f0ef9..b531775 100644
--- a/programs/pkey/rsa_verify.c
+++ b/programs/pkey/rsa_verify.c
@@ -114,7 +114,7 @@
     }
 
     i = 0;
-    while( fscanf( f, "%02X", &c ) > 0 &&
+    while( fscanf( f, "%02X", (unsigned int*) &c ) > 0 &&
            i < (int) sizeof( buf ) )
         buf[i++] = (unsigned char) c;
 
@@ -144,7 +144,7 @@
     if( ( ret = mbedtls_rsa_pkcs1_verify( &rsa, NULL, NULL, MBEDTLS_RSA_PUBLIC,
                                   MBEDTLS_MD_SHA256, 20, hash, buf ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_rsa_pkcs1_verify returned -0x%0x\n\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_rsa_pkcs1_verify returned -0x%0x\n\n", (unsigned int) -ret );
         goto exit;
     }
 
diff --git a/programs/psa/key_ladder_demo.c b/programs/psa/key_ladder_demo.c
index f492e0e..1dbbc81 100644
--- a/programs/psa/key_ladder_demo.c
+++ b/programs/psa/key_ladder_demo.c
@@ -101,7 +101,7 @@
         status = ( expr );                                      \
         if( status != PSA_SUCCESS )                             \
         {                                                       \
-            printf( "Error %d at line %u: %s\n",                \
+            printf( "Error %d at line %d: %s\n",                \
                     (int) status,                               \
                     __LINE__,                                   \
                     #expr );                                    \
diff --git a/programs/random/gen_entropy.c b/programs/random/gen_entropy.c
index 6ae63b7..c60aec9 100644
--- a/programs/random/gen_entropy.c
+++ b/programs/random/gen_entropy.c
@@ -80,7 +80,7 @@
         if( ret != 0 )
         {
             mbedtls_printf( "  failed\n  !  mbedtls_entropy_func returned -%04X\n",
-                            ret );
+                            (unsigned int) ret );
             goto cleanup;
         }
 
diff --git a/programs/ssl/dtls_client.c b/programs/ssl/dtls_client.c
index 3ea2a68..ce1056f 100644
--- a/programs/ssl/dtls_client.c
+++ b/programs/ssl/dtls_client.c
@@ -149,7 +149,7 @@
                           mbedtls_test_cas_pem_len );
     if( ret < 0 )
     {
-        mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -225,7 +225,7 @@
 
     if( ret != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -303,7 +303,7 @@
                 goto close_notify;
 
             default:
-                mbedtls_printf( " mbedtls_ssl_read returned -0x%x\n\n", -ret );
+                mbedtls_printf( " mbedtls_ssl_read returned -0x%x\n\n", (unsigned int) -ret );
                 goto exit;
         }
     }
diff --git a/programs/ssl/dtls_server.c b/programs/ssl/dtls_server.c
index bb32724..f63741f 100644
--- a/programs/ssl/dtls_server.c
+++ b/programs/ssl/dtls_server.c
@@ -291,7 +291,7 @@
                     client_ip, cliip_len ) ) != 0 )
     {
         printf( " failed\n  ! "
-                "mbedtls_ssl_set_client_transport_id() returned -0x%x\n\n", -ret );
+                "mbedtls_ssl_set_client_transport_id() returned -0x%x\n\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -318,7 +318,7 @@
     }
     else if( ret != 0 )
     {
-        printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n", -ret );
+        printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n", (unsigned int) -ret );
         goto reset;
     }
 
@@ -351,7 +351,7 @@
                 goto close_notify;
 
             default:
-                printf( " mbedtls_ssl_read returned -0x%x\n\n", -ret );
+                printf( " mbedtls_ssl_read returned -0x%x\n\n", (unsigned int) -ret );
                 goto reset;
         }
     }
diff --git a/programs/ssl/ssl_client1.c b/programs/ssl/ssl_client1.c
index b723243..3724c64 100644
--- a/programs/ssl/ssl_client1.c
+++ b/programs/ssl/ssl_client1.c
@@ -134,7 +134,7 @@
                           mbedtls_test_cas_pem_len );
     if( ret < 0 )
     {
-        mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -203,7 +203,7 @@
     {
         if( ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE )
         {
-            mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n", -ret );
+            mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n", (unsigned int) -ret );
             goto exit;
         }
     }
diff --git a/programs/ssl/ssl_client2.c b/programs/ssl/ssl_client2.c
index 73a9933..6b09a89 100644
--- a/programs/ssl/ssl_client2.c
+++ b/programs/ssl/ssl_client2.c
@@ -833,7 +833,7 @@
                 break;
 
             default:
-                mbedtls_printf( "mbedtls_ssl_check_record() failed fatally with -%#04x.\n", -ret );
+                mbedtls_printf( "mbedtls_ssl_check_record() failed fatally with -%#04x.\n", (unsigned int) -ret );
                 return( -1 );
         }
 
@@ -1077,7 +1077,7 @@
     if( ret != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_ssl_get_peer_cid returned -0x%x\n\n",
-                        -ret );
+                        (unsigned int) -ret );
         return( ret );
     }
 
@@ -1101,7 +1101,7 @@
         if( ret != 0 )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ssl_get_peer_cid returned -0x%x\n\n",
-                            -ret );
+                            (unsigned int) -ret );
             return( ret );
         }
 
@@ -1111,7 +1111,7 @@
         if( ret != 0 )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ssl_get_peer_cid returned -0x%x\n\n",
-                            -ret );
+                            (unsigned int) -ret );
             return( ret );
         }
         mbedtls_printf( "(%s) Peer CID (length %u Bytes): ",
@@ -2013,7 +2013,7 @@
                                            strlen( pers ) ) ) != 0 )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%x\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
     }
@@ -2024,7 +2024,7 @@
                                            strlen( pers ) ) ) != 0 )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%x\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
     }
@@ -2082,7 +2082,7 @@
     if( ret < 0 )
     {
         mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n",
-                        -ret );
+                        (unsigned int) -ret );
         goto exit;
     }
 
@@ -2117,7 +2117,7 @@
     if( ret != 0 )
     {
         mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n",
-                        -ret );
+                        (unsigned int) -ret );
         goto exit;
     }
 
@@ -2142,7 +2142,7 @@
     if( ret != 0 )
     {
         mbedtls_printf( " failed\n  !  mbedtls_pk_parse_key returned -0x%x\n\n",
-                        -ret );
+                        (unsigned int) -ret );
         goto exit;
     }
 
@@ -2179,7 +2179,7 @@
                        MBEDTLS_NET_PROTO_TCP : MBEDTLS_NET_PROTO_UDP ) ) != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_net_connect returned -0x%x\n\n",
-                        -ret );
+                        (unsigned int) -ret );
         goto exit;
     }
 
@@ -2190,7 +2190,7 @@
     if( ret != 0 )
     {
         mbedtls_printf( " failed\n  ! net_set_(non)block() returned -0x%x\n\n",
-                        -ret );
+                        (unsigned int) -ret );
         goto exit;
     }
 
@@ -2208,7 +2208,7 @@
                     MBEDTLS_SSL_PRESET_DEFAULT ) ) != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_ssl_config_defaults returned -0x%x\n\n",
-                        -ret );
+                        (unsigned int) -ret );
         goto exit;
     }
 
@@ -2249,7 +2249,7 @@
         if( ret != 0 )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ssl_conf_cid_len returned -%#04x\n\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
     }
@@ -2447,7 +2447,7 @@
     if( ( ret = mbedtls_ssl_setup( &ssl, &conf ) ) != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_ssl_setup returned -0x%x\n\n",
-                        -ret );
+                        (unsigned int) -ret );
         goto exit;
     }
 
@@ -2527,7 +2527,7 @@
             ret != MBEDTLS_ERR_SSL_CRYPTO_IN_PROGRESS )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n",
-                            -ret );
+                            (unsigned int) -ret );
             if( ret == MBEDTLS_ERR_X509_CERT_VERIFY_FAILED )
                 mbedtls_printf(
                     "    Unable to verify the server's certificate. "
@@ -2599,7 +2599,7 @@
                                          != 0 )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ssl_tls_prf returned -0x%x\n\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
 
@@ -2620,7 +2620,7 @@
                                          sizeof( eap_tls_iv ) ) ) != 0 )
          {
              mbedtls_printf( " failed\n  ! mbedtls_ssl_tls_prf returned -0x%x\n\n",
-                             -ret );
+                             (unsigned int) -ret );
              goto exit;
          }
 
@@ -2667,7 +2667,7 @@
                                                   &session_data_len ) ) != 0 )
             {
                 mbedtls_printf( " failed\n  ! mbedtls_ssl_session_saved returned -0x%04x\n\n",
-                                -ret );
+                                (unsigned int) -ret );
                 goto exit;
             }
         }
@@ -2676,7 +2676,7 @@
             if( ( ret = mbedtls_ssl_get_session( &ssl, &saved_session ) ) != 0 )
             {
                 mbedtls_printf( " failed\n  ! mbedtls_ssl_get_session returned -0x%x\n\n",
-                                -ret );
+                                (unsigned int) -ret );
                 goto exit;
             }
         }
@@ -2827,7 +2827,7 @@
                     ret != MBEDTLS_ERR_SSL_CRYPTO_IN_PROGRESS )
                 {
                     mbedtls_printf( " failed\n  ! mbedtls_ssl_write returned -0x%x\n\n",
-                                    -ret );
+                                    (unsigned int) -ret );
                     goto exit;
                 }
 
@@ -2955,7 +2955,7 @@
 
                     default:
                         mbedtls_printf( " mbedtls_ssl_read returned -0x%x\n",
-                                        -ret );
+                                        (unsigned int) -ret );
                         goto exit;
                 }
             }
@@ -3019,7 +3019,7 @@
                     goto close_notify;
 
                 default:
-                    mbedtls_printf( " mbedtls_ssl_read returned -0x%x\n", -ret );
+                    mbedtls_printf( " mbedtls_ssl_read returned -0x%x\n", (unsigned int) -ret );
                     goto exit;
             }
         }
@@ -3047,7 +3047,7 @@
         if( ( ret = mbedtls_ssl_session_reset( &ssl ) ) != 0 )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ssl_session_reset returned -0x%x\n\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
 
@@ -3058,7 +3058,7 @@
                 ret != MBEDTLS_ERR_SSL_CRYPTO_IN_PROGRESS )
             {
                 mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n",
-                                -ret );
+                                (unsigned int) -ret );
                 goto exit;
             }
 
@@ -3092,7 +3092,7 @@
         if( ret != MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ssl_context_save returned "
-                            "-0x%x\n\n", -ret );
+                            "-0x%x\n\n", (unsigned int) -ret );
 
             goto exit;
         }
@@ -3110,7 +3110,7 @@
                                               buf_len, &buf_len ) ) != 0 )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ssl_context_save returned "
-                            "-0x%x\n\n", -ret );
+                            "-0x%x\n\n", (unsigned int) -ret );
 
             goto exit;
         }
@@ -3139,7 +3139,7 @@
                                                context_buf, buf_len ) ) != 0 )
             {
                 mbedtls_printf( "failed\n  ! mbedtls_base64_encode returned "
-                            "-0x%x\n", -ret );
+                            "-0x%x\n", (unsigned int) -ret );
                 mbedtls_free( b64_buf );
                 goto exit;
             }
@@ -3184,7 +3184,7 @@
             if( ( ret = mbedtls_ssl_setup( &ssl, &conf ) ) != 0 )
             {
                 mbedtls_printf( " failed\n  ! mbedtls_ssl_setup returned "
-                                "-0x%x\n\n", -ret );
+                                "-0x%x\n\n", (unsigned int) -ret );
                 goto exit;
             }
 
@@ -3211,7 +3211,7 @@
                                               buf_len ) ) != 0 )
         {
             mbedtls_printf( "failed\n  ! mbedtls_ssl_context_load returned "
-                            "-0x%x\n\n", -ret );
+                            "-0x%x\n\n", (unsigned int) -ret );
 
             goto exit;
         }
@@ -3283,7 +3283,7 @@
         if( ( ret = mbedtls_ssl_session_reset( &ssl ) ) != 0 )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ssl_session_reset returned -0x%x\n\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
 
@@ -3294,7 +3294,7 @@
                                                   session_data_len ) ) != 0 )
             {
                 mbedtls_printf( " failed\n  ! mbedtls_ssl_session_load returned -0x%x\n\n",
-                                -ret );
+                                (unsigned int) -ret );
                 goto exit;
             }
         }
@@ -3302,7 +3302,7 @@
         if( ( ret = mbedtls_ssl_set_session( &ssl, &saved_session ) ) != 0 )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ssl_set_session returned -0x%x\n\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
 
@@ -3312,7 +3312,7 @@
                         MBEDTLS_NET_PROTO_TCP : MBEDTLS_NET_PROTO_UDP ) ) != 0 )
         {
             mbedtls_printf( " failed\n  ! mbedtls_net_connect returned -0x%x\n\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
 
@@ -3323,7 +3323,7 @@
         if( ret != 0 )
         {
             mbedtls_printf( " failed\n  ! net_set_(non)block() returned -0x%x\n\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
 
@@ -3334,7 +3334,7 @@
                 ret != MBEDTLS_ERR_SSL_CRYPTO_IN_PROGRESS )
             {
                 mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n",
-                                -ret );
+                                (unsigned int) -ret );
                 goto exit;
             }
         }
@@ -3353,7 +3353,7 @@
     {
         char error_buf[100];
         mbedtls_strerror( ret, error_buf, 100 );
-        mbedtls_printf("Last error was: -0x%X - %s\n\n", -ret, error_buf );
+        mbedtls_printf("Last error was: -0x%X - %s\n\n", (unsigned int) -ret, error_buf );
     }
 #endif
 
diff --git a/programs/ssl/ssl_server.c b/programs/ssl/ssl_server.c
index 3e1d9a4..9668cf9 100644
--- a/programs/ssl/ssl_server.c
+++ b/programs/ssl/ssl_server.c
@@ -309,7 +309,7 @@
                     break;
 
                 default:
-                    mbedtls_printf( " mbedtls_ssl_read returned -0x%x\n", -ret );
+                    mbedtls_printf( " mbedtls_ssl_read returned -0x%x\n", (unsigned int) -ret );
                     break;
             }
 
diff --git a/programs/ssl/ssl_server2.c b/programs/ssl/ssl_server2.c
index 1d03fe2..ca557ca 100644
--- a/programs/ssl/ssl_server2.c
+++ b/programs/ssl/ssl_server2.c
@@ -932,7 +932,7 @@
                 break;
 
             default:
-                mbedtls_printf( "mbedtls_ssl_check_record() failed fatally with -%#04x.\n", -ret );
+                mbedtls_printf( "mbedtls_ssl_check_record() failed fatally with -%#04x.\n", (unsigned int) -ret );
                 return( -1 );
         }
 
@@ -1720,7 +1720,7 @@
     if( ret != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_ssl_get_peer_cid returned -0x%x\n\n",
-                        -ret );
+                        (unsigned int) -ret );
         return( ret );
     }
 
@@ -2755,7 +2755,7 @@
                                            strlen( pers ) ) ) != 0 )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%x\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
     }
@@ -2766,7 +2766,7 @@
                                            strlen( pers ) ) ) != 0 )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%x\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
     }
@@ -2823,7 +2823,7 @@
 #endif /* MBEDTLS_CERTS_C */
     if( ret < 0 )
     {
-        mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -2842,7 +2842,7 @@
         if( ( ret = mbedtls_x509_crt_parse_file( &srvcert, opt.crt_file ) ) != 0 )
         {
             mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse_file returned -0x%x\n\n",
-                    -ret );
+                    (unsigned int) -ret );
             goto exit;
         }
     }
@@ -2851,7 +2851,7 @@
         key_cert_init++;
         if( ( ret = mbedtls_pk_parse_keyfile( &pkey, opt.key_file, "" ) ) != 0 )
         {
-            mbedtls_printf( " failed\n  !  mbedtls_pk_parse_keyfile returned -0x%x\n\n", -ret );
+            mbedtls_printf( " failed\n  !  mbedtls_pk_parse_keyfile returned -0x%x\n\n", (unsigned int) -ret );
             goto exit;
         }
     }
@@ -2867,7 +2867,7 @@
         if( ( ret = mbedtls_x509_crt_parse_file( &srvcert2, opt.crt_file2 ) ) != 0 )
         {
             mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse_file(2) returned -0x%x\n\n",
-                    -ret );
+                    (unsigned int) -ret );
             goto exit;
         }
     }
@@ -2877,7 +2877,7 @@
         if( ( ret = mbedtls_pk_parse_keyfile( &pkey2, opt.key_file2, "" ) ) != 0 )
         {
             mbedtls_printf( " failed\n  !  mbedtls_pk_parse_keyfile(2) returned -0x%x\n\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
     }
@@ -2904,7 +2904,7 @@
                                     mbedtls_test_srv_crt_rsa_len ) ) != 0 )
         {
             mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
         if( ( ret = mbedtls_pk_parse_key( &pkey,
@@ -2912,7 +2912,7 @@
                                   mbedtls_test_srv_key_rsa_len, NULL, 0 ) ) != 0 )
         {
             mbedtls_printf( " failed\n  !  mbedtls_pk_parse_key returned -0x%x\n\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
         key_cert_init = 2;
@@ -2923,7 +2923,7 @@
                                     mbedtls_test_srv_crt_ec_len ) ) != 0 )
         {
             mbedtls_printf( " failed\n  !  x509_crt_parse2 returned -0x%x\n\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
         if( ( ret = mbedtls_pk_parse_key( &pkey2,
@@ -2931,7 +2931,7 @@
                                   mbedtls_test_srv_key_ec_len, NULL, 0 ) ) != 0 )
         {
             mbedtls_printf( " failed\n  !  pk_parse_key2 returned -0x%x\n\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
         key_cert_init2 = 2;
@@ -2951,7 +2951,7 @@
         if( ( ret = mbedtls_dhm_parse_dhmfile( &dhm, opt.dhm_file ) ) != 0 )
         {
             mbedtls_printf( " failed\n  ! mbedtls_dhm_parse_dhmfile returned -0x%04X\n\n",
-                     -ret );
+                     (unsigned int) -ret );
             goto exit;
         }
 
@@ -2988,7 +2988,7 @@
                           opt.transport == MBEDTLS_SSL_TRANSPORT_STREAM ?
                           MBEDTLS_NET_PROTO_TCP : MBEDTLS_NET_PROTO_UDP ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_net_bind returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_net_bind returned -0x%x\n\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -3005,7 +3005,7 @@
                     opt.transport,
                     MBEDTLS_SSL_PRESET_DEFAULT ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_ssl_config_defaults returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_ssl_config_defaults returned -0x%x\n\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -3064,7 +3064,7 @@
         if( ret != 0 )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ssl_conf_cid_len returned -%#04x\n\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
     }
@@ -3390,7 +3390,7 @@
                                      strlen( opt.psk_identity ) );
             if( ret != 0 )
             {
-                mbedtls_printf( "  failed\n  mbedtls_ssl_conf_psk returned -0x%04X\n\n", - ret );
+                mbedtls_printf( "  failed\n  mbedtls_ssl_conf_psk returned -0x%04X\n\n", (unsigned int) -ret );
                 goto exit;
             }
         }
@@ -3431,7 +3431,7 @@
 #endif
     if( ret != 0 )
     {
-        mbedtls_printf( "  failed\n  mbedtls_ssl_conf_dh_param returned -0x%04X\n\n", - ret );
+        mbedtls_printf( "  failed\n  mbedtls_ssl_conf_dh_param returned -0x%04X\n\n", (unsigned int) -ret );
         goto exit;
     }
 #endif
@@ -3444,7 +3444,7 @@
 
     if( ( ret = mbedtls_ssl_setup( &ssl, &conf ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_ssl_setup returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_ssl_setup returned -0x%x\n\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -3529,7 +3529,7 @@
         }
 #endif
 
-        mbedtls_printf( " failed\n  ! mbedtls_net_accept returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_net_accept returned -0x%x\n\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -3539,7 +3539,7 @@
         ret = mbedtls_net_set_block( &client_fd );
     if( ret != 0 )
     {
-        mbedtls_printf( " failed\n  ! net_set_(non)block() returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  ! net_set_(non)block() returned -0x%x\n\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -3552,7 +3552,7 @@
                         client_ip, cliip_len ) ) != 0 )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ssl_set_client_transport_id() returned -0x%x\n\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
     }
@@ -3615,7 +3615,7 @@
     }
     else if( ret != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n", (unsigned int) -ret );
 
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
         if( ret == MBEDTLS_ERR_X509_CERT_VERIFY_FAILED )
@@ -3709,7 +3709,7 @@
                                          != 0 )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ssl_tls_prf returned -0x%x\n\n",
-                            -ret );
+                            (unsigned int) -ret );
             goto exit;
         }
 
@@ -3730,7 +3730,7 @@
                                          sizeof( eap_tls_iv ) ) ) != 0 )
          {
              mbedtls_printf( " failed\n  ! mbedtls_ssl_tls_prf returned -0x%x\n\n",
-                             -ret );
+                             (unsigned int) -ret );
              goto exit;
          }
 
@@ -3821,7 +3821,7 @@
                         goto reset;
 
                     default:
-                        mbedtls_printf( " mbedtls_ssl_read returned -0x%x\n", -ret );
+                        mbedtls_printf( " mbedtls_ssl_read returned -0x%x\n", (unsigned int) -ret );
                         goto reset;
                 }
             }
@@ -3867,7 +3867,7 @@
                 }
 
                 larger_buf[ori_len + extra_len] = '\0';
-                mbedtls_printf( " %u bytes read (%u + %u)\n\n%s\n",
+                mbedtls_printf( " %d bytes read (%d + %d)\n\n%s\n",
                         ori_len + extra_len, ori_len, extra_len,
                         (char *) larger_buf );
 
@@ -3935,7 +3935,7 @@
                     goto close_notify;
 
                 default:
-                    mbedtls_printf( " mbedtls_ssl_read returned -0x%x\n", -ret );
+                    mbedtls_printf( " mbedtls_ssl_read returned -0x%x\n", (unsigned int) -ret );
                     goto reset;
             }
         }
@@ -4092,7 +4092,7 @@
         if( ret != MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ssl_context_save returned "
-                            "-0x%x\n\n", -ret );
+                            "-0x%x\n\n", (unsigned int) -ret );
 
             goto exit;
         }
@@ -4110,7 +4110,7 @@
                                               buf_len, &buf_len ) ) != 0 )
         {
             mbedtls_printf( " failed\n  ! mbedtls_ssl_context_save returned "
-                            "-0x%x\n\n", -ret );
+                            "-0x%x\n\n", (unsigned int) -ret );
 
             goto exit;
         }
@@ -4139,7 +4139,7 @@
                                                context_buf, buf_len ) ) != 0 )
             {
                 mbedtls_printf( "failed\n  ! mbedtls_base64_encode returned "
-                            "-0x%x\n", -ret );
+                            "-0x%x\n", (unsigned int) -ret );
                 mbedtls_free( b64_buf );
                 goto exit;
             }
@@ -4199,7 +4199,7 @@
             if( ( ret = mbedtls_ssl_setup( &ssl, &conf ) ) != 0 )
             {
                 mbedtls_printf( " failed\n  ! mbedtls_ssl_setup returned "
-                                "-0x%x\n\n", -ret );
+                                "-0x%x\n\n", (unsigned int) -ret );
                 goto exit;
             }
 
@@ -4232,7 +4232,7 @@
                                               buf_len ) ) != 0 )
         {
             mbedtls_printf( "failed\n  ! mbedtls_ssl_context_load returned "
-                            "-0x%x\n\n", -ret );
+                            "-0x%x\n\n", (unsigned int) -ret );
 
             goto exit;
         }
@@ -4275,7 +4275,7 @@
     {
         char error_buf[100];
         mbedtls_strerror( ret, error_buf, 100 );
-        mbedtls_printf("Last error was: -0x%X - %s\n\n", -ret, error_buf );
+        mbedtls_printf("Last error was: -0x%X - %s\n\n", (unsigned int) -ret, error_buf );
     }
 #endif
 
diff --git a/programs/test/benchmark.c b/programs/test/benchmark.c
index 57e8e7e..1575930 100644
--- a/programs/test/benchmark.c
+++ b/programs/test/benchmark.c
@@ -112,7 +112,7 @@
         mbedtls_printf( "FAILED: %s\n", tmp );
 #else
 #define PRINT_ERROR                                                     \
-        mbedtls_printf( "FAILED: -0x%04x\n", -ret );
+        mbedtls_printf( "FAILED: -0x%04x\n", (unsigned int) -ret );
 #endif
 
 #define TIME_AND_TSC( TITLE, CODE )                                     \
diff --git a/programs/test/udp_proxy.c b/programs/test/udp_proxy.c
index 7447571..d601dcc 100644
--- a/programs/test/udp_proxy.c
+++ b/programs/test/udp_proxy.c
@@ -456,7 +456,7 @@
     {
         if( ( ret = ctx_buffer_flush( buf ) ) <= 0 )
         {
-            mbedtls_printf( "ctx_buffer_flush failed with -%#04x", -ret );
+            mbedtls_printf( "ctx_buffer_flush failed with -%#04x", (unsigned int) -ret );
             return( ret );
         }
     }
@@ -495,7 +495,7 @@
     ret = mbedtls_net_send( ctx, data, len );
     if( ret < 0 )
     {
-        mbedtls_printf( "net_send returned -%#04x\n", -ret );
+        mbedtls_printf( "net_send returned -%#04x\n", (unsigned int) -ret );
     }
     return( ret );
 }
@@ -999,7 +999,7 @@
     {
         char error_buf[100];
         mbedtls_strerror( ret, error_buf, 100 );
-        mbedtls_printf( "Last error was: -0x%04X - %s\n\n", - ret, error_buf );
+        mbedtls_printf( "Last error was: -0x%04X - %s\n\n", (unsigned int) -ret, error_buf );
         fflush( stdout );
     }
 #endif
diff --git a/programs/util/strerror.c b/programs/util/strerror.c
index 458280c..b0487c0 100644
--- a/programs/util/strerror.c
+++ b/programs/util/strerror.c
@@ -79,7 +79,7 @@
     {
         char error_buf[200];
         mbedtls_strerror( val, error_buf, 200 );
-        mbedtls_printf("Last error was: -0x%04x - %s\n\n", (int) -val, error_buf );
+        mbedtls_printf("Last error was: -0x%04x - %s\n\n", (unsigned int) -val, error_buf );
     }
 
 #if defined(_WIN32)
diff --git a/programs/x509/cert_app.c b/programs/x509/cert_app.c
index 432eefb..7723a37 100644
--- a/programs/x509/cert_app.c
+++ b/programs/x509/cert_app.c
@@ -258,7 +258,7 @@
     {
         if( ( ret = mbedtls_x509_crt_parse_path( &cacert, opt.ca_path ) ) < 0 )
         {
-            mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse_path returned -0x%x\n\n", -ret );
+            mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse_path returned -0x%x\n\n", (unsigned int) -ret );
             goto exit;
         }
 
@@ -268,7 +268,7 @@
     {
         if( ( ret = mbedtls_x509_crt_parse_file( &cacert, opt.ca_file ) ) < 0 )
         {
-            mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse_file returned -0x%x\n\n", -ret );
+            mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse_file returned -0x%x\n\n", (unsigned int) -ret );
             goto exit;
         }
 
@@ -282,7 +282,7 @@
     {
         if( ( ret = mbedtls_x509_crl_parse_file( &cacrl, opt.crl_file ) ) != 0 )
         {
-            mbedtls_printf( " failed\n  !  mbedtls_x509_crl_parse returned -0x%x\n\n", -ret );
+            mbedtls_printf( " failed\n  !  mbedtls_x509_crl_parse returned -0x%x\n\n", (unsigned int) -ret );
             goto exit;
         }
 
diff --git a/programs/x509/cert_write.c b/programs/x509/cert_write.c
index d36d73c..9a7dc59 100644
--- a/programs/x509/cert_write.c
+++ b/programs/x509/cert_write.c
@@ -507,7 +507,7 @@
     {
         mbedtls_strerror( ret, buf, 1024 );
         mbedtls_printf( " failed\n  !  mbedtls_mpi_read_string "
-                        "returned -0x%04x - %s\n\n", -ret, buf );
+                        "returned -0x%04x - %s\n\n", (unsigned int) -ret, buf );
         goto exit;
     }
 
@@ -527,7 +527,7 @@
         {
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse_file "
-                            "returned -0x%04x - %s\n\n", -ret, buf );
+                            "returned -0x%04x - %s\n\n", (unsigned int) -ret, buf );
             goto exit;
         }
 
@@ -537,7 +537,7 @@
         {
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  mbedtls_x509_dn_gets "
-                            "returned -0x%04x - %s\n\n", -ret, buf );
+                            "returned -0x%04x - %s\n\n", (unsigned int) -ret, buf );
             goto exit;
         }
 
@@ -561,7 +561,7 @@
         {
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  mbedtls_x509_csr_parse_file "
-                            "returned -0x%04x - %s\n\n", -ret, buf );
+                            "returned -0x%04x - %s\n\n", (unsigned int) -ret, buf );
             goto exit;
         }
 
@@ -571,7 +571,7 @@
         {
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  mbedtls_x509_dn_gets "
-                            "returned -0x%04x - %s\n\n", -ret, buf );
+                            "returned -0x%04x - %s\n\n", (unsigned int) -ret, buf );
             goto exit;
         }
 
@@ -596,7 +596,7 @@
         {
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  mbedtls_pk_parse_keyfile "
-                            "returned -0x%04x - %s\n\n", -ret, buf );
+                            "returned -0x%04x - %s\n\n", (unsigned int) -ret, buf );
             goto exit;
         }
 
@@ -612,7 +612,7 @@
     {
         mbedtls_strerror( ret, buf, 1024 );
         mbedtls_printf( " failed\n  !  mbedtls_pk_parse_keyfile "
-                        "returned -x%02x - %s\n\n", -ret, buf );
+                        "returned -x%02x - %s\n\n", (unsigned int) -ret, buf );
         goto exit;
     }
 
@@ -646,7 +646,7 @@
     {
         mbedtls_strerror( ret, buf, 1024 );
         mbedtls_printf( " failed\n  !  mbedtls_x509write_crt_set_subject_name "
-                        "returned -0x%04x - %s\n\n", -ret, buf );
+                        "returned -0x%04x - %s\n\n", (unsigned int) -ret, buf );
         goto exit;
     }
 
@@ -654,7 +654,7 @@
     {
         mbedtls_strerror( ret, buf, 1024 );
         mbedtls_printf( " failed\n  !  mbedtls_x509write_crt_set_issuer_name "
-                        "returned -0x%04x - %s\n\n", -ret, buf );
+                        "returned -0x%04x - %s\n\n", (unsigned int) -ret, buf );
         goto exit;
     }
 
@@ -669,7 +669,7 @@
     {
         mbedtls_strerror( ret, buf, 1024 );
         mbedtls_printf( " failed\n  !  mbedtls_x509write_crt_set_serial "
-                        "returned -0x%04x - %s\n\n", -ret, buf );
+                        "returned -0x%04x - %s\n\n", (unsigned int) -ret, buf );
         goto exit;
     }
 
@@ -678,7 +678,7 @@
     {
         mbedtls_strerror( ret, buf, 1024 );
         mbedtls_printf( " failed\n  !  mbedtls_x509write_crt_set_validity "
-                        "returned -0x%04x - %s\n\n", -ret, buf );
+                        "returned -0x%04x - %s\n\n", (unsigned int) -ret, buf );
         goto exit;
     }
 
@@ -696,7 +696,7 @@
         {
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  x509write_crt_set_basic_contraints "
-                            "returned -0x%04x - %s\n\n", -ret, buf );
+                            "returned -0x%04x - %s\n\n", (unsigned int) -ret, buf );
             goto exit;
         }
 
@@ -716,7 +716,7 @@
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  mbedtls_x509write_crt_set_subject"
                             "_key_identifier returned -0x%04x - %s\n\n",
-                            -ret, buf );
+                            (unsigned int) -ret, buf );
             goto exit;
         }
 
@@ -735,7 +735,7 @@
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  mbedtls_x509write_crt_set_authority_"
                             "key_identifier returned -0x%04x - %s\n\n",
-                            -ret, buf );
+                            (unsigned int) -ret, buf );
             goto exit;
         }
 
@@ -754,7 +754,7 @@
         {
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  mbedtls_x509write_crt_set_key_usage "
-                            "returned -0x%04x - %s\n\n", -ret, buf );
+                            "returned -0x%04x - %s\n\n", (unsigned int) -ret, buf );
             goto exit;
         }
 
@@ -772,7 +772,7 @@
         {
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  mbedtls_x509write_crt_set_ns_cert_type "
-                            "returned -0x%04x - %s\n\n", -ret, buf );
+                            "returned -0x%04x - %s\n\n", (unsigned int) -ret, buf );
             goto exit;
         }
 
@@ -790,7 +790,7 @@
     {
         mbedtls_strerror( ret, buf, 1024 );
         mbedtls_printf( " failed\n  !  write_certificate -0x%04x - %s\n\n",
-                        -ret, buf );
+                        (unsigned int) -ret, buf );
         goto exit;
     }
 
diff --git a/scripts/data_files/error.fmt b/scripts/data_files/error.fmt
index 0e128e8..97b74bc 100644
--- a/scripts/data_files/error.fmt
+++ b/scripts/data_files/error.fmt
@@ -113,7 +113,7 @@
         high_level_error_description = mbedtls_high_level_strerr( ret );
 
         if( high_level_error_description == NULL )
-            mbedtls_snprintf( buf, buflen, "UNKNOWN ERROR CODE (%04X)", use_ret );
+            mbedtls_snprintf( buf, buflen, "UNKNOWN ERROR CODE (%04X)", (unsigned int) use_ret );
         else
             mbedtls_snprintf( buf, buflen, "%s", high_level_error_description );
 
@@ -150,7 +150,7 @@
     low_level_error_description = mbedtls_low_level_strerr( ret );
 
     if( low_level_error_description == NULL )
-        mbedtls_snprintf( buf, buflen, "UNKNOWN ERROR CODE (%04X)", use_ret );
+        mbedtls_snprintf( buf, buflen, "UNKNOWN ERROR CODE (%04X)", (unsigned int) use_ret );
     else
         mbedtls_snprintf( buf, buflen, "%s", low_level_error_description );
 }
diff --git a/tests/suites/test_suite_version.function b/tests/suites/test_suite_version.function
index 10f9e11..7d59794 100644
--- a/tests/suites/test_suite_version.function
+++ b/tests/suites/test_suite_version.function
@@ -52,7 +52,7 @@
     mbedtls_version_get_string( get_str );
     mbedtls_version_get_string_full( get_str_full );
 
-    mbedtls_snprintf( build_str, 100, "%d.%d.%d",
+    mbedtls_snprintf( build_str, 100, "%u.%u.%u",
         (get_int >> 24) & 0xFF,
         (get_int >> 16) & 0xFF,
         (get_int >> 8) & 0xFF );
diff --git a/tests/suites/test_suite_x509parse.function b/tests/suites/test_suite_x509parse.function
index 85ff41d..f3e83d6 100644
--- a/tests/suites/test_suite_x509parse.function
+++ b/tests/suites/test_suite_x509parse.function
@@ -237,7 +237,7 @@
     char *p = *buf;
     size_t n = *size;
 
-    ret = mbedtls_snprintf( p, n, "type : %u", san->type );
+    ret = mbedtls_snprintf( p, n, "type : %d", san->type );
     MBEDTLS_X509_SAFE_SNPRINTF;
 
     switch( san->type )