diff --git a/Gemfile.lock b/Gemfile.lock
index 7e6fbc9..2b8ae26 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -44,6 +44,7 @@ GEM
     mini_portile2 (2.4.0)
     minitest (5.11.3)
     multi_json (1.13.1)
+    nio4r (2.5.8)
     nokogiri (1.10.3)
       mini_portile2 (~> 2.4.0)
     pg (0.21.0)
@@ -51,7 +52,8 @@ GEM
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
     public_suffix (3.0.3)
-    puma (3.12.1)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (1.6.11)
     rack-protection (1.5.5)
       rack