diff --git a/karma.conf.js b/karma.conf.js
index 0425750..6cde869 100644
--- a/karma.conf.js
+++ b/karma.conf.js
@@ -37,8 +37,7 @@ module.exports = config => {
       debug: true
     },
     files: ['test/*'],
-    frameworks: ['browserify', 'chai', 'mocha', 'polyfill', 'sinon'],
-    polyfill: ['Promise'],
+    frameworks: ['browserify', 'chai', 'mocha', 'sinon'],
     preprocessors: {
       'test/*': ['browserify']
     },
diff --git a/package.json b/package.json
index a367690..95960aa 100644
--- a/package.json
+++ b/package.json
@@ -16,11 +16,11 @@
     "@rollup/plugin-commonjs": "^11.0.2",
     "browserify": "^16.5.0",
     "chai": "*",
+    "core-js": "^3.6.4",
     "karma": "^4.4.1",
     "karma-browserify": "^7.0.0",
     "karma-chai": "^0.1.0",
     "karma-mocha": "^1.3.0",
-    "karma-polyfill": "^1.0.0",
     "karma-sauce-launcher": "^1.2.0",
     "karma-sinon": "^1.0.5",
     "lodash": "^4.17.15",
diff --git a/test/promise.js b/test/promise.js
index 3ff7c39..d814b28 100644
--- a/test/promise.js
+++ b/test/promise.js
@@ -1,6 +1,8 @@
+/* eslint-disable import/no-unassigned-import */
 /* eslint-disable no-unused-expressions */
 /* eslint-disable promise/prefer-await-to-then */
 
+require('core-js/features/promise');
 var _ = require('lodash');
 
 var jsonp = require('../promise');