diff --git a/mkvmuxer.cpp b/mkvmuxer.cpp
index d245fbd..56d9fee 100644
--- a/mkvmuxer.cpp
+++ b/mkvmuxer.cpp
@@ -612,6 +612,10 @@ bool Track::Write(IMkvWriter* writer) const {
   if (!writer)
     return false;
 
+  // mandatory elements without a default value.
+  if (!type_ || !codec_id_)
+    return false;
+
   // |size| may be bigger than what is written out in this function because
   // derived classes may write out more data in the Track element.
   const uint64 payload_size = PayloadSize();
@@ -619,10 +623,6 @@ bool Track::Write(IMkvWriter* writer) const {
   if (!WriteEbmlMasterElement(writer, kMkvTrackEntry, payload_size))
     return false;
 
-  // |type_| has to be specified before the Track can be written.
-  if (!type_)
-    return false;
-
   uint64 size = EbmlElementSize(kMkvTrackNumber, number_);
   size += EbmlElementSize(kMkvTrackUID, uid_);
   size += EbmlElementSize(kMkvTrackType, type_);