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;
     }