diff --git a/bower.json b/bower.json
index f9573e2..984a730 100644
--- a/bower.json
+++ b/bower.json
@@ -10,6 +10,9 @@
   "keywords": [
     "mutationobservers"
   ],
+  "dependencies": {
+    "Polymer/WeakMap": ">=0.0.20131107"
+  },
   "license": "BSD",
   "private": true,
   "ignore": [