diff --git a/Gemfile.lock b/Gemfile.lock
index cf47c04..cca054b 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -103,7 +103,8 @@ GEM
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
     public_suffix (3.0.2)
-    puma (3.11.4)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     pygments.rb (1.2.1)
       multi_json (>= 1.0.0)
     racc (1.4.14)