diff --git a/mb_string.gemspec b/mb_string.gemspec
index 30c87a8..d5dfde0 100644
--- a/mb_string.gemspec
+++ b/mb_string.gemspec
@@ -22,7 +22,7 @@ Gem::Specification.new do |spec|
   spec.add_dependency "unicode-display_width", "~> 1.3.0"
 
   spec.add_development_dependency "bundler"
-  spec.add_development_dependency "rake", "~> 11.3.0"
+  spec.add_development_dependency "rake", "~> 12.3.1"
   spec.add_development_dependency "rspec", "~> 3.7.0"
   spec.add_development_dependency "simplecov", "~> 0.12.0"