diff --git a/lib/liquid/lexer.rb b/lib/liquid/lexer.rb
index e00a80a..c584bb8 100644
--- a/lib/liquid/lexer.rb
+++ b/lib/liquid/lexer.rb
@@ -1,3 +1,4 @@
+require "strscan"
 module Liquid
   class Token
     attr_accessor :type, :contents