diff --git a/kubeclient.gemspec b/kubeclient.gemspec
index 4f2be1f3..b2b26b02 100644
--- a/kubeclient.gemspec
+++ b/kubeclient.gemspec
@@ -29,6 +29,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'googleauth', '~> 0.5'
   spec.add_development_dependency('mocha', '~> 1.5')
   spec.add_development_dependency 'openid_connect', '~> 1.1'
+  spec.add_development_dependency 'net-smtp'
 
   spec.add_dependency 'faraday', '~> 1.1'
   spec.add_dependency 'faraday_middleware', '~> 1.0'