diff --git a/lib/fluent/engine.rb b/lib/fluent/engine.rb
index aa18ac7d57..d5551221ae 100644
--- a/lib/fluent/engine.rb
+++ b/lib/fluent/engine.rb
@@ -25,6 +25,9 @@
 
 module Fluent
   class EngineClass
+    # For compat. remove it in fluentd v2
+    include Fluent::MessagePackFactory::Mixin
+
     def initialize
       @root_agent = nil
       @default_loop = nil