diff --git a/lib/haml/util.rb b/lib/haml/util.rb
index <HASH>..<HASH> 100644
--- a/lib/haml/util.rb
+++ b/lib/haml/util.rb
@@ -3,8 +3,7 @@ require 'set'
 require 'enumerator'
 require 'stringio'
 require 'haml/root'
-
-require 'haml/util/subset_heap'
+require 'haml/util/subset_map'
 
 module Haml
   # A module containing various useful functions.
[Sass] Require subset_map, not subset_heap.