diff --git a/src/output/output.cpp b/src/output/output.cpp
index c3c59c34..2286a3d0 100644
--- a/src/output/output.cpp
+++ b/src/output/output.cpp
@@ -169,6 +169,7 @@ namespace Mist {
   }
 
   void Output::bufferPacket(JSON::Value & pack){
+    if (!pack["trackid"].asInt()){return;}
     if (myMeta.tracks[pack["trackid"].asInt()].type != "video"){
       if ((pack["time"].asInt() - bookKeeping[trackMap[pack["trackid"].asInt()]].lastKeyTime) >= 5000){
         pack["keyframe"] = 1LL;