diff --git a/Gemfile.lock b/Gemfile.lock
index 7563f28..2c6e101 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -7,7 +7,9 @@ GEM
     diff-lcs (1.3)
     docile (1.1.5)
     json (2.1.0)
-    puma (3.12.4)
+    nio4r (2.5.8)
+    puma (4.3.9)
+      nio4r (~> 2.0)
     rack (1.6.13)
     rack-console (1.3.1)
       rack (>= 1.1)