2 files changed, 6 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) {
diff --git a/lib/strerror.c b/lib/strerror.c
index 29df5aa55..a7b761800 100644
--- a/lib/strerror.c
+++ b/lib/strerror.c
@@ -392,6 +392,9 @@ curl_multi_strerror(CURLMcode error)
   case CURLM_WAKEUP_FAILURE:
     return "Wakeup is unavailable or failed";
 
+  case CURLM_BAD_FUNCTION_ARGUMENT:
+    return "A libcurl function was given a bad argument";
+
   case CURLM_LAST:
     break;
   }