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;
         }