diff --git a/html/index.erb b/html/index.erb
index 6f21e3e5..bcbcff91 100644
--- a/html/index.erb
+++ b/html/index.erb
@@ -17,7 +17,7 @@
 <%
   def parse str
     # credit to: http://stackoverflow.com/q/3128406/154508
-    tokens = str.scan(/#{Regexp.escape("(")}|#{Regexp.escape(")")}|[a-zA-Z0-9\-\_\+]+/)
+    tokens = str.scan(/#{Regexp.escape("(")}|#{Regexp.escape(")")}|[a-zA-Z0-9\'\-\_\+]+/)
 
     stack = [[]]