diff --git a/CHANGELOG.md b/CHANGELOG.md
index 994e65bf..712f8e48 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,12 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+## [1.33.0] - 2021-05-04
+
+## Fixed
+
+- Fix timeout dialog on IE by adding polyfill for Number.isNaN
+
 ## [1.32.0] - 2021-04-29
 
 ## Fixed
diff --git a/check-compatibility.js b/check-compatibility.js
index 655a5975..7c17e987 100644
--- a/check-compatibility.js
+++ b/check-compatibility.js
@@ -14,7 +14,7 @@ if (!knownPrototypeKitNames.includes(consumerPackageJson.name)) {
 }
 
 const compatibility = {
-  1.30: {
+  1.33: {
     'prototype-kit': ['9.12', '9.11', '9.10', '9.9', '9.8', '9.7', '9.6', '9.5', '9.4', '9.3', '9.2', '9.1', '9.0', '9.9', '9.10', '9.11'],
   },
   0.6: {
diff --git a/package-lock.json b/package-lock.json
index 5e708342..eb247e8b 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "hmrc-frontend",
-  "version": "1.31.0",
+  "version": "1.33.0",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
diff --git a/package.json b/package.json
index b3921eed..ecb548d0 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "hmrc-frontend",
-  "version": "1.32.0",
+  "version": "1.33.0",
   "description": "Design patterns for HMRC frontends",
   "scripts": {
     "start": "gulp dev",
diff --git a/src/components/timeout-dialog/validate-input.js b/src/components/timeout-dialog/validate-input.js
index db8c2320..2c3c898a 100644
--- a/src/components/timeout-dialog/validate-input.js
+++ b/src/components/timeout-dialog/validate-input.js
@@ -1,3 +1,5 @@
+import '../../vendor/polyfills/Number/prototype/isNaN';
+
 function ValidateInput() {
 }
 
diff --git a/src/vendor/polyfills/Number/prototype/isNaN.js b/src/vendor/polyfills/Number/prototype/isNaN.js
new file mode 100644
index 00000000..aaa1a017
--- /dev/null
+++ b/src/vendor/polyfills/Number/prototype/isNaN.js
@@ -0,0 +1,4 @@
+// Polyfill from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isNaN
+Number.isNaN = Number.isNaN || function isNaN(input) {
+  return typeof input === 'number' && input !== input;
+}