diff --git a/Parser.go b/Parser.go
index 907ba39..e1eb9e3 100644
--- a/Parser.go
+++ b/Parser.go
@@ -122,7 +122,7 @@ func parseNextBox(reader io.Reader, filePosition uint64) (box interface{}, endPo
 		box, err = ParseTrackFragmentRunBox(filePosition, boxHeaderSize, boxContentBytes)
 	default:
 		logger.Println("unknown box type", boxType, "at", filePosition)
-		err = errors.New("unknown box type " + boxType)
+		return nil, filePosition, false, errors.New("unknown box type " + boxType)
 	}
 
 	// check for box errors