diff --git a/core/modules/ckeditor5/tests/src/Kernel/SmartDefaultSettingsTest.php b/core/modules/ckeditor5/tests/src/Kernel/SmartDefaultSettingsTest.php
index 5b1d2d998e..5e4896b1ba 100644
--- a/core/modules/ckeditor5/tests/src/Kernel/SmartDefaultSettingsTest.php
+++ b/core/modules/ckeditor5/tests/src/Kernel/SmartDefaultSettingsTest.php
@@ -573,7 +573,10 @@ public function provider() {
           'ckeditor5_sourceEditing' => [
             'allowed_tags' => array_merge(
               $basic_html_test_case['expected_ckeditor5_settings']['plugins']['ckeditor5_sourceEditing']['allowed_tags'],
-              ['<drupal-media data-caption>'],
+              [
+                '<img loading>',
+                '<drupal-media data-caption>',
+              ],
             ),
           ],
         ] + $basic_html_test_case['expected_ckeditor5_settings']['plugins'],
@@ -581,7 +584,7 @@ public function provider() {
       'expected_superset' => $basic_html_test_case['expected_superset'],
       'expected_fundamental_compatibility_violations' => $basic_html_test_case['expected_fundamental_compatibility_violations'],
       'expected_messages' => array_merge($basic_html_test_case['expected_messages'], [
-        "This format's HTML filters includes plugins that support the following tags, but not some of their attributes. To ensure these attributes remain supported by this text format, the following were added to the Source Editing plugin's <em>Manually editable HTML tags</em>: &lt;a hreflang&gt; &lt;blockquote cite&gt; &lt;ul type&gt; &lt;ol start type&gt; &lt;h2 id&gt; &lt;h3 id&gt; &lt;h4 id&gt; &lt;h5 id&gt; &lt;h6 id&gt; &lt;drupal-media data-caption&gt;.",
+        "This format's HTML filters includes plugins that support the following tags, but not some of their attributes. To ensure these attributes remain supported by this text format, the following were added to the Source Editing plugin's <em>Manually editable HTML tags</em>: &lt;a hreflang&gt; &lt;blockquote cite&gt; &lt;ul type&gt; &lt;ol start type&gt; &lt;h2 id&gt; &lt;h3 id&gt; &lt;h4 id&gt; &lt;h5 id&gt; &lt;h6 id&gt; &lt;img loading&gt; &lt;drupal-media data-caption&gt;.",
       ]),
     ];