diff --git a/fluent-plugin-events/Gemfile.lock b/fluent-plugin-events/Gemfile.lock
index 341aa2d..78971a9 100644
--- a/fluent-plugin-events/Gemfile.lock
+++ b/fluent-plugin-events/Gemfile.lock
@@ -82,7 +82,7 @@ GEM
     http-parser (1.2.3)
       ffi-compiler (>= 1.0, < 2.0)
     http_parser.rb (0.8.0)
-    mocha (2.3.0)
+    mocha (2.4.0)
       ruby2_keywords (>= 0.0.5)
     msgpack (1.5.1)
     multipart-post (2.4.1)