diff --git a/Gemfile.lock b/Gemfile.lock
index cea404f..2ddcad3 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -98,7 +98,8 @@ GEM
       mini_portile2 (~> 2.4.0)
     nokogiri (1.10.8-x86-mingw32)
       mini_portile2 (~> 2.4.0)
-    puma (3.12.4)
+    puma (4.3.9)
+      nio4r (~> 2.0)
     rack (2.2.2)
     rack-test (0.6.3)
       rack (>= 1.0)