diff --git a/lib/jekyll/utils.rb b/lib/jekyll/utils.rb
index 86d24cef..c30a986a 100644
--- a/lib/jekyll/utils.rb
+++ b/lib/jekyll/utils.rb
@@ -34,6 +34,10 @@ module Jekyll
         target[key] = overwrite[key]
       end
 
+      if target.default_proc.nil?
+        target.default_proc = overwrite.default_proc
+      end
+
       target
     end