diff --git a/lib/file-list.js b/lib/file-list.js
index ca9c9e2e2..25a813f7c 100644
--- a/lib/file-list.js
+++ b/lib/file-list.js
@@ -7,7 +7,8 @@
 // Dependencies
 // ------------
 
-require('core-js')
+var Map = require('core-js/library/fn/map')
+var Set = require('core-js/library/fn/set')
 var from = require('core-js/library/fn/array/from')
 var Promise = require('bluebird')
 var mm = require('minimatch')