diff --git a/lib/chai/core/assertions.js b/lib/chai/core/assertions.js
index 71baf3a99..2e8f807cf 100644
--- a/lib/chai/core/assertions.js
+++ b/lib/chai/core/assertions.js
@@ -3178,7 +3178,7 @@ module.exports = function (chai, _) {
     } else {
       if (isDeep) {
         this.assert(
-          list.some(possibility => _.eql(expected, possibility))
+          list.some(function(possibility) { return _.eql(expected, possibility) })
           , 'expected #{this} to deeply equal one of #{exp}'
           , 'expected #{this} to deeply equal one of #{exp}'
           , list