diff --git a/benchmarks/fluentd/Gemfile.lock b/benchmarks/fluentd/Gemfile.lock
index 06712b91..8894e106 100644
--- a/benchmarks/fluentd/Gemfile.lock
+++ b/benchmarks/fluentd/Gemfile.lock
@@ -98,6 +98,7 @@ DEPENDENCIES
   base64
   csv
   fluentd
+  yajl-ruby!
 
 CHECKSUMS
   async (2.24.0) sha256=589d11ac6d5808da195ed5ac71f37afcab505855aa958bf5fc463a5469c34377