diff --git a/graphql.gemspec b/graphql.gemspec
index 9ba3edc6fc..e7efb6c458 100644
--- a/graphql.gemspec
+++ b/graphql.gemspec
@@ -48,4 +48,5 @@ Gem::Specification.new do |s|
   s.add_development_dependency "m", "~> 1.5.0"
   s.add_development_dependency "webrick"
   s.add_development_dependency "csv"
+  s.add_development_dependency "base64"
 end