diff --git a/suo.gemspec b/suo.gemspec
index a2352d0..190c1ae 100644
--- a/suo.gemspec
+++ b/suo.gemspec
@@ -25,7 +25,7 @@ Gem::Specification.new do |spec|
   spec.add_dependency "redis"
   spec.add_dependency "msgpack"
 
-  spec.add_development_dependency "bundler", "~> 1.5"
+  spec.add_development_dependency "bundler", "~> 2"
   spec.add_development_dependency "rake", "~> 10.0"
   spec.add_development_dependency "rubocop", "~> 0.49.0"
   spec.add_development_dependency "minitest", "~> 5.5.0"