diff --git a/lib/fluent/plugin/out_tdlog.rb b/lib/fluent/plugin/out_tdlog.rb
index fccc22d..819e655 100644
--- a/lib/fluent/plugin/out_tdlog.rb
+++ b/lib/fluent/plugin/out_tdlog.rb
@@ -1,4 +1,5 @@
 require 'fileutils'
+require 'json'
 require 'tempfile'
 require 'zlib'
 require 'stringio'
@@ -136,7 +137,7 @@ def format(tag, time, record)
     end
 
     def summarize_record(record)
-      json = Yajl.dump(record)
+      json = JSON.generate(record)
       if json.size > 100
         json[0..97] + "..."
       else