diff --git a/middleman-core/lib/middleman-core/extension.rb b/middleman-core/lib/middleman-core/extension.rb
index 887a05fb..48653bef 100644
--- a/middleman-core/lib/middleman-core/extension.rb
+++ b/middleman-core/lib/middleman-core/extension.rb
@@ -1,5 +1,6 @@
 require 'active_support/core_ext/module/delegation'
 require 'active_support/core_ext/class/attribute'
+require 'middleman-core/configuration'
 
 module Middleman
   class Extension