diff --git a/lib/formdata.c b/lib/formdata.c
index e03d75aea8..91ad34c0a9 100644
--- a/lib/formdata.c
+++ b/lib/formdata.c
@@ -931,7 +931,7 @@ void curl_formfree(struct curl_httppost *form)
   required to be reentrant is not required to be thread-safe.
 
 */
-char *basename(char *path)
+static char *basename(char *path)
 {
   /* Ignore all the details above for now and make a quick and simple
      implementaion here */