diff --git a/karma.conf.js b/karma.conf.js
index 9f05b3e2c9..4e6e33ddfc 100644
--- a/karma.conf.js
+++ b/karma.conf.js
@@ -32,7 +32,7 @@ const hostname = os.hostname();
 const SAUCE_BROWSER_PLATFORM_MAP = {
   'chrome@latest': 'Windows 10',
   'MicrosoftEdge@latest': 'Windows 10',
-  'internet explorer@latest': 'Windows 10',
+  // 'internet explorer@latest': 'Windows 10',
   'firefox@latest': 'Windows 10',
   'safari@latest': 'macOS 10.13'
 };
diff --git a/rollup.config.js b/rollup.config.js
index c10b485ab0..156e1cf2e8 100644
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -4,7 +4,7 @@ import json from '@rollup/plugin-json';
 import nodePolyfills from 'rollup-plugin-node-polyfills';
 import globals from 'rollup-plugin-node-globals';
 
-import {babel} from '@rollup/plugin-babel';
+// import {babel} from '@rollup/plugin-babel';
 
 // Debugging tools
 import visualizer from 'rollup-plugin-visualizer';
@@ -17,10 +17,10 @@ const config = {
   output: {
     file: './mocha.js',
     format: 'umd',
-    sourcemap: true,
+    // sourcemap: true,
     name: 'mocha',
-    banner: `// mocha@${version} transpiled to javascript ES5`,
-    intro: 'var regeneratorRuntime;'
+    banner: `// mocha@${version} in javascript ES2018`
+    // intro: 'var regeneratorRuntime;'
   },
   plugins: [
     json(),
@@ -32,25 +32,25 @@ const config = {
     nodePolyfills(),
     nodeResolve({
       browser: true
-    }),
-    babel({
-      exclude: /core-js/,
-      presets: [
-        [
-          '@babel/preset-env',
-          {
-            modules: false,
-            useBuiltIns: 'usage',
-            forceAllTransforms: true,
-            corejs: {
-              version: 3,
-              proposals: false
-            }
-          }
-        ]
-      ],
-      babelHelpers: 'bundled'
     })
+    // babel({
+    //   exclude: /core-js/,
+    //   presets: [
+    //     [
+    //       '@babel/preset-env',
+    //       {
+    //         modules: false,
+    //         useBuiltIns: 'usage',
+    //         forceAllTransforms: true,
+    //         corejs: {
+    //           version: 3,
+    //           proposals: false
+    //         }
+    //       }
+    //     ]
+    //   ],
+    //   babelHelpers: 'bundled'
+    // })
   ],
   onwarn: (warning, warn) => {
     if (warning.code === 'CIRCULAR_DEPENDENCY') return;