diff --git a/libs/blocks/marketo/marketo.js b/libs/blocks/marketo/marketo.js
index e496345174..a6cfb7a2e7 100644
--- a/libs/blocks/marketo/marketo.js
+++ b/libs/blocks/marketo/marketo.js
@@ -32,6 +32,8 @@ export const formValidate = (form) => {
 };
 
 export const decorateURL = (destination, baseURL = window.location) => {
+  if (!(destination.startsWith('http') || destination.startsWith('/'))) return null;
+
   try {
     let destinationUrl = new URL(destination, baseURL.origin);
     const { hostname, pathname, search, hash } = destinationUrl;
diff --git a/test/blocks/marketo/marketo.test.js b/test/blocks/marketo/marketo.test.js
index f3ab41549c..b986b6b2cb 100644
--- a/test/blocks/marketo/marketo.test.js
+++ b/test/blocks/marketo/marketo.test.js
@@ -97,4 +97,10 @@ describe('marketo decorateURL', () => {
     const result = decorateURL('/marketo-block/thank-you', baseURL);
     expect(result).to.equal('https://business.adobe.com/uk/marketo-block/thank-you.html');
   });
+
+  it('Does not decorate non-url text', () => {
+    const baseURL = new URL('https://business.adobe.com/marketo-block.html');
+    const result = decorateURL('Thank you for submitting the form', baseURL);
+    expect(result).to.be.null;
+  });
 });