diff --git a/fluent-plugin-prometheus-format/Gemfile.lock b/fluent-plugin-prometheus-format/Gemfile.lock
index 7b27876..79a0b1e 100644
--- a/fluent-plugin-prometheus-format/Gemfile.lock
+++ b/fluent-plugin-prometheus-format/Gemfile.lock
@@ -24,7 +24,7 @@ GEM
     http_parser.rb (0.8.0)
     msgpack (1.5.1)
     power_assert (2.0.3)
-    rake (13.0.6)
+    rake (13.1.0)
     serverengine (2.3.2)
       sigdump (~> 0.2.2)
     sigdump (0.2.5)