diff --git a/Gemfile.lock b/Gemfile.lock
index ece6bbf..7be7fef 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -174,6 +174,7 @@ GEM
     neat (1.7.4)
       bourbon (>= 4.0)
       sass (>= 3.3)
+    nio4r (2.5.8)
     nokogiri (1.6.7.2)
       mini_portile2 (~> 2.0.0.rc2)
     normalize-rails (3.0.3)
@@ -194,7 +195,8 @@ GEM
     premailer-rails (1.9.2)
       actionmailer (>= 3, < 6)
       premailer (~> 1.7, >= 1.7.9)
-    puma (3.4.0)
+    puma (4.3.11)
+      nio4r (~> 2.0)
     rabl (0.11.8)
       activesupport (>= 2.3.14)
     rack (1.6.4)