diff --git a/packages/common/locales/package.json b/packages/common/locales/package.json
index 6baf80d756..47fd7ad86e 100644
--- a/packages/common/locales/package.json
+++ b/packages/common/locales/package.json
@@ -1,4 +1,4 @@
 {
   "description": "This directory contains UMD files which by its nature are not side-effect free. The parent package.json marks the whole @angular/common package as side-effect free, so if this directory is not excluded from that, build-optimizer will mark the contents as side-effect free and uglify will incorrectly remove all needed localization code.",
-  "sideEffects": false
+  "sideEffects": true
 }