diff --git a/materials/canonical/session19/WebApp/Gemfile.lock b/materials/canonical/session19/WebApp/Gemfile.lock
index 222db1c..de4ed4a 100644
--- a/materials/canonical/session19/WebApp/Gemfile.lock
+++ b/materials/canonical/session19/WebApp/Gemfile.lock
@@ -3,7 +3,7 @@ GEM
   specs:
     mustermann (3.0.0)
       ruby2_keywords (~> 0.0.1)
-    rack (2.2.8)
+    rack (2.2.8.1)
     rack-protection (3.1.0)
       rack (~> 2.2, >= 2.2.4)
     ruby2_keywords (0.0.5)