diff --git a/Gemfile.lock b/Gemfile.lock
index ce00e58..ef7a33a 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -79,7 +79,8 @@ GEM
     nio4r (2.3.1)
     nokogiri (1.10.3)
       mini_portile2 (~> 2.4.0)
-    puma (3.12.1)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.0.7)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)