1 files changed, 3 insertions, 0 deletions
diff --git a/lib/multi.c b/lib/multi.c
index 6d819b4aa..31275ca2b 100644
--- a/lib/multi.c
+++ b/lib/multi.c
@@ -1048,6 +1048,9 @@ static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
   if(multi->in_callback)
     return CURLM_RECURSIVE_API_CALL;
 
+  if(timeout_ms < 0)
+    return CURLM_BAD_FUNCTION_ARGUMENT;
+
   /* Count up how many fds we have from the multi handle */
   data = multi->easyp;
   while(data) {