diff --git a/programs/pkey/pk_verify.c b/programs/pkey/pk_verify.c
index a6d4901..a1a2389 100644
--- a/programs/pkey/pk_verify.c
+++ b/programs/pkey/pk_verify.c
@@ -132,8 +132,11 @@
     mbedtls_pk_free( &pk );
 
 #if defined(MBEDTLS_ERROR_C)
-    mbedtls_strerror( ret, (char *) buf, sizeof(buf) );
-    mbedtls_printf( "  !  Last error was: %s\n", buf );
+    if( ret != 0 )
+    {
+        mbedtls_strerror( ret, (char *) buf, sizeof(buf) );
+        mbedtls_printf( "  !  Last error was: %s\n", buf );
+    }
 #endif
 
 #if defined(_WIN32)