diff --git a/Gemfile b/Gemfile
index 382252d..7441b52 100644
--- a/Gemfile
+++ b/Gemfile
@@ -7,7 +7,7 @@ group :test do
 end
 
 group :cookstyle do
-  gem "cookstyle", "~> 8.7"
+  gem "cookstyle", "~> 9.0"
 end
 
 group :docs do