diff --git a/zip_code_jp.gemspec b/zip_code_jp.gemspec
index 39fc6357..4139332a 100644
--- a/zip_code_jp.gemspec
+++ b/zip_code_jp.gemspec
@@ -18,7 +18,7 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ["lib"]
 
-  spec.add_development_dependency "bundler", "~> 1.3"
+  spec.add_development_dependency "bundler", ">= 2.1.0"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "rspec"
   spec.add_development_dependency "pry"