diff --git a/middleman-core/lib/middleman-core/renderers/redcarpet.rb b/middleman-core/lib/middleman-core/renderers/redcarpet.rb
index 623d9d54..eb722f6d 100644
--- a/middleman-core/lib/middleman-core/renderers/redcarpet.rb
+++ b/middleman-core/lib/middleman-core/renderers/redcarpet.rb
@@ -1,4 +1,5 @@
 require 'redcarpet'
+require 'active_support/core_ext/module/attribute_accessors'
 
 module Middleman
   module Renderers