diff --git a/Gemfile.lock b/Gemfile.lock
index e306965dfcc..7131838609f 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -145,6 +145,7 @@ GEM
     minitest (5.11.3)
     multi_json (1.13.1)
     multipart-post (2.0.0)
+    nio4r (2.5.8)
     nokogiri (1.8.5)
       mini_portile2 (~> 2.3.0)
     padrino-helpers (0.12.9)
@@ -163,7 +164,8 @@ GEM
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
     public_suffix (3.0.3)
-    puma (3.11.4)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (1.6.11)
     rack-jekyll (0.5.0)
       jekyll (>= 1.3)