diff --git a/Gemfile.lock b/Gemfile.lock
index 17f0be0..ac8b4d3 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -78,7 +78,8 @@ GEM
     nio4r (2.0.0)
     nokogiri (1.7.0.1)
       mini_portile2 (~> 2.1.0)
-    puma (3.8.2)
+    puma (4.3.9)
+      nio4r (~> 2.0)
     rack (2.0.1)
     rack-test (0.6.3)
       rack (>= 1.0)