diff --git a/webapp/ruby/Gemfile.lock b/webapp/ruby/Gemfile.lock
index 6404314..d5dc481 100644
--- a/webapp/ruby/Gemfile.lock
+++ b/webapp/ruby/Gemfile.lock
@@ -13,7 +13,9 @@ GEM
     multi_json (1.12.2)
     mustermann (1.0.1)
     mysql2 (0.4.10)
-    puma (3.10.0)
+    nio4r (2.5.8)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.0.3)
     rack-protection (2.0.0)
       rack