diff --git a/Gemfile.lock b/Gemfile.lock
index 5f00fb5..2561d80 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -148,6 +148,7 @@ GEM
     moped (1.5.3)
     multi_json (1.15.0)
     multipart-post (2.0.0)
+    nio4r (2.5.8)
     nokogiri (1.8.2)
       mini_portile2 (~> 2.3.0)
     origin (1.1.0)
@@ -167,7 +168,8 @@ GEM
       coderay (~> 1.0.5)
       method_source (~> 0.8)
       slop (~> 3.4)
-    puma (3.6.2)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (1.4.7)
     rack-cache (1.7.1)
       rack (>= 0.4)