diff --git a/db/memtable.cc b/db/memtable.cc
index f42774d..4f09340 100644
--- a/db/memtable.cc
+++ b/db/memtable.cc
@@ -78,6 +78,7 @@ void MemTable::Add(SequenceNumber s, ValueType type, const Slice& key,
   // Format of an entry is concatenation of:
   //  key_size     : varint32 of internal_key.size()
   //  key bytes    : char[internal_key.size()]
+  //  tag          : uint64((sequence << 8) | type)
   //  value_size   : varint32 of value.size()
   //  value bytes  : char[value.size()]
   size_t key_size = key.size();