diff --git a/lib/bundler/rubygems_ext.rb b/lib/bundler/rubygems_ext.rb
index 53a153e560c..608c15745db 100644
--- a/lib/bundler/rubygems_ext.rb
+++ b/lib/bundler/rubygems_ext.rb
@@ -19,6 +19,7 @@
 end
 
 require "bundler/match_platform"
+require "bundler/plugin/api/source"
 
 module Gem
   @loaded_stacks = Hash.new {|h, k| h[k] = [] }