diff --git a/lib/liquid/document.rb b/lib/liquid/document.rb
index b802c85..241ea61 100644
--- a/lib/liquid/document.rb
+++ b/lib/liquid/document.rb
@@ -8,7 +8,7 @@ module Liquid
 
     # There isn't a real delimiter
     def block_delimiter
-      []
+      nil
     end
 
     # Document blocks don't need to be terminated since they are not actually opened