diff --git a/lib/fluent/event.rb b/lib/fluent/event.rb
index db644ccf4d..b124d6d886 100644
--- a/lib/fluent/event.rb
+++ b/lib/fluent/event.rb
@@ -308,11 +308,13 @@ def ensure_decompressed!
   end
 
   module ChunkMessagePackEventStreamer
-    # chunk.extend(ChunkEventStreamer)
+    # chunk.extend(ChunkMessagePackEventStreamer)
     #  => chunk.each{|time, record| ... }
     def each(unpacker: nil, &block)
       open do |io|
-        (unpacker || Fluent::MessagePackFactory.msgpack_unpacker(io)).each(&block)
+        # Note: If need to use `unpacker`, then implement it,
+        # e.g., `unpacker.feed_each(io.read, &block)` (Not tested)
+        Fluent::MessagePackFactory.msgpack_unpacker(io).each(&block)
       end
       nil
     end