diff --git a/libs/features/personalization/personalization.js b/libs/features/personalization/personalization.js
index 4116d17d9d..cd571934b4 100644
--- a/libs/features/personalization/personalization.js
+++ b/libs/features/personalization/personalization.js
@@ -417,7 +417,7 @@ async function getPersonalizationVariant(manifestPath, variantNames = [], varian
   if (config.mep?.override) {
     let manifest;
     /* c8 ignore start */
-    config.mep?.override?.split(',').some((item) => {
+    config.mep?.override?.split('---').some((item) => {
       const pair = item.trim().split('--');
       if (pair[0] === manifestPath && pair.length > 1) {
         [, manifest] = pair;
diff --git a/libs/features/personalization/preview.js b/libs/features/personalization/preview.js
index c17923241c..2fe0e790fe 100644
--- a/libs/features/personalization/preview.js
+++ b/libs/features/personalization/preview.js
@@ -28,7 +28,7 @@ function updatePreviewButton() {
   });
 
   const simulateHref = new URL(window.location.href);
-  simulateHref.searchParams.set('mep', manifestParameter.join(','));
+  simulateHref.searchParams.set('mep', manifestParameter.join('---'));
 
   const mepHighlightCheckbox = document.querySelector(
     '.mep-popup input[type="checkbox"]#mepHighlightCheckbox',
@@ -203,7 +203,7 @@ function createPreviewPill(manifests) {
   const personalizationOn = getMetadata('personalization');
   const personalizationOnText = personalizationOn && personalizationOn !== '' ? 'on' : 'off';
   const simulateHref = new URL(window.location.href);
-  simulateHref.searchParams.set('manifest', manifestParameter.join(','));
+  simulateHref.searchParams.set('manifest', manifestParameter.join('---'));
 
   const config = getConfig();
   let mepHighlightChecked = '';
diff --git a/test/features/personalization/preview.test.js b/test/features/personalization/preview.test.js
index b3b9b13c70..51feed86e1 100644
--- a/test/features/personalization/preview.test.js
+++ b/test/features/personalization/preview.test.js
@@ -185,6 +185,7 @@ describe('preview feature', () => {
     expect(document.querySelector('input#mepHighlightCheckbox').getAttribute('checked')).to.equal('checked');
   });
   it('updates preview button', () => {
+    expect(document.querySelector('a[title="Preview above choices"]').getAttribute('href')).to.contain('---');
     document.querySelector('#new-manifest').value = 'https://main--homepage--adobecom.hlx.live/homepage/fragments/mep/new-manifest.json';
     document.querySelector('input[name="/homepage/fragments/mep/selected-example.json"][value="default"]').click();
     expect(document.querySelector('a[title="Preview above choices"]').getAttribute('href')).to.contain('new-manifest.json');
@@ -193,6 +194,7 @@ describe('preview feature', () => {
     expect(document.querySelector('a[title="Preview above choices"]').getAttribute('href')).to.not.contain('mepHighlight');
     document.querySelector('input#mepPreviewButtonCheckbox').click();
     expect(document.querySelector('a[title="Preview above choices"]').getAttribute('href')).to.contain('mepButton=off');
+    expect(document.querySelector('a[title="Preview above choices"]').getAttribute('href')).to.contain('---');
   });
   it('opens manifest', () => {
     document.querySelector('a.mep-edit-manifest').click();