diff --git a/lib/setopt.c b/lib/setopt.c
index 0c3ccb5a00..2f601a8335 100644
--- a/lib/setopt.c
+++ b/lib/setopt.c
@@ -2916,6 +2916,6 @@ CURLcode curl_easy_setopt(CURL *curl, CURLoption option, ...)
 
   va_end(arg);
   if(result == CURLE_BAD_FUNCTION_ARGUMENT)
-    failf(data, "setopt 0x%x got bad argument", option);
+    failf(data, "setopt 0x%x got bad argument", (unsigned int)option);
   return result;
 }