diff --git a/src/ui/Gemfile.lock b/src/ui/Gemfile.lock
index d5d5400..f937880 100644
--- a/src/ui/Gemfile.lock
+++ b/src/ui/Gemfile.lock
@@ -29,9 +29,11 @@ GEM
     multi_json (1.13.1)
     multipart-post (2.0.0)
     mustermann (1.0.3)
+    nio4r (2.5.8)
     prometheus-client (0.8.0)
       quantile (~> 0.2.1)
-    puma (3.12.0)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     quantile (0.2.1)
     raabro (1.1.6)
     rack (2.0.6)
@@ -77,7 +79,7 @@ DEPENDENCIES
   haml
   prometheus-client
   puma
-  rack (>= 2.0.6)
+  rack
   rufus-scheduler
   sinatra (~> 2.0.2)
   sinatra-contrib