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;
     }