diff --git a/base.json b/base.json
index e4d98e1efa..65ff848e27 100644
--- a/base.json
+++ b/base.json
@@ -1,5 +1,7 @@
 {
 
+  "ambiguate-properties": true,
+
   "checks": {
     "accessControls": "ERROR",
     "visibility": "ERROR",
@@ -19,6 +21,8 @@
     "goog.DEBUG": false
   },
 
+  "disambiguate-properties": true,
+
   "externs": [
     "externs/bingmaps.js",
     "externs/proj4js.js",