diff --git a/bower.json b/bower.json
index e385125..6f90b3d 100644
--- a/bower.json
+++ b/bower.json
@@ -10,8 +10,8 @@
     "HTMLImports"
   ],
   "dependencies": {
-    "MutationObservers": "Polymer/MutationObservers#master",
-    "tools": "Polymer/tools#master"
+    "MutationObservers": "Polymer/MutationObservers#>=0.3.0 <1.0.0",
+    "tools": "Polymer/tools#>=0.3.0 <1.0.0"
   },
   "license": "BSD",
   "private": true,
@@ -22,4 +22,4 @@
     "test",
     "tests"
   ]
-}
+}
\ No newline at end of file