diff --git a/trunk/src/app/srs_app_source.cpp b/trunk/src/app/srs_app_source.cpp
index 126b2b1a3..35661bd9c 100755
--- a/trunk/src/app/srs_app_source.cpp
+++ b/trunk/src/app/srs_app_source.cpp
@@ -311,7 +311,7 @@ int SrsMessageQueue::dump_packets(int max_count, SrsSharedPtrMessage** pmsgs, in
     SrsSharedPtrMessage* last = omsgs[count - 1];
     av_start_time = last->timestamp;
     
-    if (count >= (int)msgs.size()) {
+    if (count >= nb_msgs) {
         // the pmsgs is big enough and clear msgs at most time.
         msgs.clear();
     } else {