diff --git a/activities/20210630_rubykaigi_proposal/proto2/app/Gemfile.lock b/activities/20210630_rubykaigi_proposal/proto2/app/Gemfile.lock
index d085dd8b8..736bfc880 100644
--- a/activities/20210630_rubykaigi_proposal/proto2/app/Gemfile.lock
+++ b/activities/20210630_rubykaigi_proposal/proto2/app/Gemfile.lock
@@ -6,7 +6,7 @@ GEM
     multi_json (1.15.0)
     mustermann (3.0.3)
       ruby2_keywords (~> 0.0.1)
-    rack (3.1.16)
+    rack (3.1.17)
     rack-protection (4.1.0)
       base64 (>= 0.1.0)
       logger (>= 1.6.0)