diff --git a/puppet-lint-empty_string-check.gemspec b/puppet-lint-empty_string-check.gemspec
index e58addf..9132ec3 100644
--- a/puppet-lint-empty_string-check.gemspec
+++ b/puppet-lint-empty_string-check.gemspec
@@ -21,6 +21,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'rspec', '~> 3.0'
   spec.add_development_dependency 'rspec-its', '~> 1.0'
   spec.add_development_dependency 'rspec-collection_matchers', '~> 1.0'
+  spec.add_development_dependency 'mime-types', '~> 1.0' # 2.x dropped Ruby 1.8 support
   spec.add_development_dependency 'coveralls', '~> 0.7'
   spec.add_development_dependency 'rake'
 end