diff --git a/mixer/challenge/Gemfile.lock b/mixer/challenge/Gemfile.lock
index b87be9b..5a1cbc5 100644
--- a/mixer/challenge/Gemfile.lock
+++ b/mixer/challenge/Gemfile.lock
@@ -20,7 +20,7 @@ GEM
     mustermann (1.0.3)
     optimist (3.0.0)
     power_assert (1.1.3)
-    rack (2.0.6)
+    rack (2.2.6.2)
     rack-protection (2.0.5)
       rack
     rake (10.5.0)