diff --git a/package.json b/package.json
index 0319c27..ffe3732 100644
--- a/package.json
+++ b/package.json
@@ -24,6 +24,7 @@
     "@ng-bootstrap/ng-bootstrap": "^1.0.0-beta.9",
     "bootstrap": "^4.0.0",
     "brace": "^0.11.0",
+    "classlist.js": "^1.1.20150312",
     "core-js": "^2.4.1",
     "ng2-ace-editor": "^0.3.4",
     "node-sass": "^4.7.2",
diff --git a/src/polyfills.ts b/src/polyfills.ts
index d68672f..21e81e4 100644
--- a/src/polyfills.ts
+++ b/src/polyfills.ts
@@ -19,26 +19,26 @@
  */
 
 /** IE9, IE10 and IE11 requires all of the following polyfills. **/
-// import 'core-js/es6/symbol';
-// import 'core-js/es6/object';
-// import 'core-js/es6/function';
-// import 'core-js/es6/parse-int';
-// import 'core-js/es6/parse-float';
-// import 'core-js/es6/number';
-// import 'core-js/es6/math';
-// import 'core-js/es6/string';
-// import 'core-js/es6/date';
-// import 'core-js/es6/array';
-// import 'core-js/es6/regexp';
-// import 'core-js/es6/map';
-// import 'core-js/es6/weak-map';
-// import 'core-js/es6/set';
+import 'core-js/es6/symbol';
+import 'core-js/es6/object';
+import 'core-js/es6/function';
+import 'core-js/es6/parse-int';
+import 'core-js/es6/parse-float';
+import 'core-js/es6/number';
+import 'core-js/es6/math';
+import 'core-js/es6/string';
+import 'core-js/es6/date';
+import 'core-js/es6/array';
+import 'core-js/es6/regexp';
+import 'core-js/es6/map';
+import 'core-js/es6/weak-map';
+import 'core-js/es6/set';
 
 /** IE10 and IE11 requires the following for NgClass support on SVG elements */
-// import 'classlist.js';  // Run `npm install --save classlist.js`.
+import 'classlist.js';  // Run `npm install --save classlist.js`.
 
 /** IE10 and IE11 requires the following for the Reflect API. */
-// import 'core-js/es6/reflect';
+import 'core-js/es6/reflect';
 
 
 /** Evergreen browsers require these. **/
diff --git a/yarn.lock b/yarn.lock
index 8a13e36..4dd03bf 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1072,6 +1072,10 @@ class-utils@^0.3.5:
     isobject "^3.0.0"
     static-extend "^0.1.1"
 
+classlist.js@^1.1.20150312:
+  version "1.1.20150312"
+  resolved "https://registry.yarnpkg.com/classlist.js/-/classlist.js-1.1.20150312.tgz#1d70842f7022f08d9ac086ce69e5b250f2c57789"
+
 clean-css@4.1.x:
   version "4.1.9"
   resolved "https://registry.yarnpkg.com/clean-css/-/clean-css-4.1.9.tgz#35cee8ae7687a49b98034f70de00c4edd3826301"