diff --git a/package.json b/package.json
index e1c720a1c7a..b77d37adad6 100644
--- a/package.json
+++ b/package.json
@@ -127,6 +127,7 @@
     "tldjs": "1.6.2",
     "tracking-protection": "1.1.x",
     "underscore": "1.8.3",
+    "underscore.string": "^3.3.4",
     "url-loader": "^0.5.7",
     "webtorrent-remote": "^1.0.0"
   },