--- a/dom/media/flac/FlacFrameParser.cpp
+++ b/dom/media/flac/FlacFrameParser.cpp
@@ -71,18 +71,16 @@ FlacFrameParser::DecodeHeaderBlock(const
 
   mPacketCount++;
 
   if (aPacket[0] == 'f') {
     if (mPacketCount != 1 || memcmp(br.Read(4), "fLaC", 4) ||
         br.Remaining() != FLAC_STREAMINFO_SIZE + 4) {
       return false;
     }
-    aPacket += 4;
-    aLength -= 4;
   }
   uint8_t blockHeader = br.ReadU8();
   // blockType is a misnomer as it could indicate here either a packet type
   // should it points to the start of a Flac in Ogg metadata, or an actual
   // block type as per the flac specification.
   uint32_t blockType = blockHeader & 0x7f;
   bool lastBlock = blockHeader & 0x80;