diff --git a/lib/google/api_client/discovery/schema.rb b/lib/google/api_client/discovery/schema.rb
index b628671b8..84db9992a 100644
--- a/lib/google/api_client/discovery/schema.rb
+++ b/lib/google/api_client/discovery/schema.rb
@@ -15,6 +15,7 @@
 
 require 'time'
 require 'json'
+require 'base64'
 require 'addressable/uri'
 require 'addressable/template'