--- a/testing/mochitest/mochitest.eslintrc
+++ b/testing/mochitest/mochitest.eslintrc
@@ -17,16 +17,17 @@
     "export_assertions": false,
     "finish": false,
     "getRootDirectory": false,
     "getTestFilePath": false,
     "gTestPath": false,
     "info": false,
     "is": false,
     "isnot": false,
+    "isDeeply": false,
     "ok": false,
     "promise": false,
     "registerCleanupFunction": false,
     "requestLongerTimeout": false,
     "SimpleTest": false,
     "SpecialPowers": false,
     "todo": false,
     "todo_is": false,