diff --git a/lib/multi.c b/lib/multi.c
index 2042719d06..79d44796ec 100644
--- a/lib/multi.c
+++ b/lib/multi.c
@@ -3672,9 +3672,13 @@ static void process_pending_handles(struct Curl_multi *multi)
   if(Curl_uint_bset_first(&multi->pending, &mid)) {
     do {
       struct Curl_easy *data = Curl_multi_get_easy(multi, mid);
-      DEBUGASSERT(data);
-      if(data)
+      if(data) {
         move_pending_to_connect(multi, data);
+        break;
+      }
+      /* transfer no longer known, should not happen */
+      Curl_uint_bset_remove(&multi->pending, mid);
+      DEBUGASSERT(0);
     }
     while(Curl_uint_bset_next(&multi->pending, mid, &mid));
   }