--- a/dom/media/webm/WebMBufferedParser.h
+++ b/dom/media/webm/WebMBufferedParser.h
@@ -55,20 +55,29 @@ struct WebMTimeDataOffset
 struct WebMBufferedParser
 {
   explicit WebMBufferedParser(int64_t aOffset)
     : mStartOffset(aOffset)
     , mCurrentOffset(aOffset)
     , mInitEndOffset(-1)
     , mBlockEndOffset(-1)
     , mState(READ_ELEMENT_ID)
+    , mNextState(READ_ELEMENT_ID)
     , mVIntRaw(false)
     , mLastInitStartOffset(-1)
     , mClusterSyncPos(0)
+    , mVIntLeft(0)
+    , mBlockSize(0)
+    , mClusterTimecode(0)
+    , mClusterOffset(0)
     , mClusterEndOffset(-1)
+    , mBlockOffset(0)
+    , mBlockTimecode(0)
+    , mBlockTimecodeLength(0)
+    , mSkipBytes(0)
     , mTimecodeScale(1000000)
     , mGotTimecodeScale(false)
   {
     if (mStartOffset != 0) {
       mState = FIND_CLUSTER_SYNC;
     }
   }