diff --git a/taccsite_cms/templates/nav_portal.html b/taccsite_cms/templates/nav_portal.html
index 38df8a20b..d4a9a5bc4 100644
--- a/taccsite_cms/templates/nav_portal.html
+++ b/taccsite_cms/templates/nav_portal.html
@@ -13,5 +13,22 @@
 
   const container = document.getElementById('portal-nav');
 
-  importHTML.insertFromURL('/core/markup/nav', container);
+  await importHTML.insertFromURL('/core/markup/nav', container);
+
+  /* Make (Portal) Bootstrap 5 toggle compatible with (CMS) Bootstrap 4 */
+  [ ...container.querySelectorAll('[data-bs-toggle]')].forEach(toggle => {
+    const portalUsesBootstrap5Toggle = (
+      toggle.dataset.bsToggle !== undefined &&
+      toggle.dataset.toggle === undefined
+    )
+
+    if ( portalUsesBootstrap5Toggle ) {
+      toggle.dataset.toggle = toggle.dataset.bsToggle;
+      delete toggle.dataset.bsToggle;
+      console.log(
+        'Replaced `data-bs-toggle` with `data-toggle` in `#portal-nav`.',
+        'To not need this, update Bootstrap from 4 to 5.'
+      )
+    }
+  });
 </script>