diff -u b/core/modules/media/tests/src/FunctionalJavascript/MediaSourceTestBase.php b/core/modules/media/tests/src/FunctionalJavascript/MediaSourceTestBase.php
--- b/core/modules/media/tests/src/FunctionalJavascript/MediaSourceTestBase.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaSourceTestBase.php
@@ -104,7 +104,8 @@
 
     $this->drupalGet('admin/structure/media/add');
     $page->fillField('label', $media_type_id);
-    $this->assertJsCondition("jQuery('.machine-name-value').text() === '{$media_type_id}'");
+    $this->getSession()
+      ->wait(5000, "jQuery('.machine-name-value').text() === '{$media_type_id}'");
 
     // Make sure the source is available.
     $this->assertSession()->fieldExists('Media source');