diff --git a/app/assets/javascripts/discourse/app/controllers/user-private-messages.js b/app/assets/javascripts/discourse/app/controllers/user-private-messages.js
index d5b76815e16..adef41e742e 100644
--- a/app/assets/javascripts/discourse/app/controllers/user-private-messages.js
+++ b/app/assets/javascripts/discourse/app/controllers/user-private-messages.js
@@ -44,7 +44,7 @@ export default class extends Controller {
     for (let i = this.messagesDropdownContent.length - 1; i >= 0; i--) {
       const row = this.messagesDropdownContent[i];
 
-      if (this.router.currentURL.includes(row.id)) {
+      if (this.router.currentURL.toLowerCase().includes(row.id)) {
         value = row.id;
         break;
       }
diff --git a/app/assets/javascripts/discourse/tests/acceptance/user-private-messages-test.js b/app/assets/javascripts/discourse/tests/acceptance/user-private-messages-test.js
index fbf51ef5456..26dd52bbb95 100644
--- a/app/assets/javascripts/discourse/tests/acceptance/user-private-messages-test.js
+++ b/app/assets/javascripts/discourse/tests/acceptance/user-private-messages-test.js
@@ -697,7 +697,7 @@ acceptance(
     });
 
     test("navigating between user messages route with dropdown", async function (assert) {
-      await visit("/u/charlie/messages");
+      await visit("/u/Charlie/messages");
 
       const messagesDropdown = selectKit(".user-nav-messages-dropdown");