diff --git a/package.json b/package.json
index 95d095f..35ac355 100644
--- a/package.json
+++ b/package.json
@@ -36,7 +36,7 @@
   },
   "dependencies": {
     "underscore": "~1.3.3",
-    "mapnik-reference": "https://github.com/mapnik/mapnik-reference/tarball/master",
+    "mapnik-reference": "https://github.com/mapnik/mapnik-reference/tarball/transform-functions",
     "xml2js": "~0.1.13"
   },
   "devDependencies": {