diff --git a/mail-x_smtpapi.gemspec b/mail-x_smtpapi.gemspec
index 80086ab..c4ec9ac 100644
--- a/mail-x_smtpapi.gemspec
+++ b/mail-x_smtpapi.gemspec
@@ -17,7 +17,7 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ["lib"]
 
-  spec.add_development_dependency "bundler", "~> 2.5"
+  spec.add_development_dependency "bundler", ">= 2.2.3"
   spec.add_development_dependency "rake", "~> 13.1"
   spec.add_development_dependency "minitest", "~> 5.21"