diff --git a/css/css-color/parsing/system-color-valid.html b/css/css-color/parsing/system-color-valid.html
index eea01e5d4ee60d..1174f496d6565f 100644
--- a/css/css-color/parsing/system-color-valid.html
+++ b/css/css-color/parsing/system-color-valid.html
@@ -23,6 +23,8 @@
 test_valid_value("color", "Highlight", "highlight");
 test_valid_value("color", "HighlightText", "highlighttext");
 test_valid_value("color", "LinkText", "linktext");
+test_valid_value("color", "Mark", "mark");
+test_valid_value("color", "MarkText", "marktext");
 test_valid_value("color", "VisitedText", "visitedtext");
 test_valid_value("color", "SelectedItem", "selecteditem");
 test_valid_value("color", "SelectedItemText", "selecteditemtext");
diff --git a/css/css-color/system-color-consistency.html b/css/css-color/system-color-consistency.html
index f8fc5ef0d00ec9..c714adc2c1ec63 100644
--- a/css/css-color/system-color-consistency.html
+++ b/css/css-color/system-color-consistency.html
@@ -19,12 +19,16 @@
   <div id="buttons">
     <button name="button"></button><input type="submit" name="submit button"><input type="reset" name="reset button">
   </div>
+  <mark id="mark">Marked text</mark>
   <script>
     for (let element of document.getElementById("buttons").children) {
       style = document.defaultView.getComputedStyle(element);
       test_computed_value(`color`, `ButtonText`, style.getPropertyValue('color'), 'has the same color as text on a ' + element.name);
     }
-    // Test with no specified target contrast
+    // Mark and MarkText
+    style = document.defaultView.getComputedStyle(document.getElementById('mark'));
+    test_computed_value('color', 'Mark', style.getPropertyValue('background-color'), 'has the same color as the background-color of a mark element');
+    test_computed_value('color', 'MarkText', style.getPropertyValue('color'), 'has the same color as the color of a mark element');
   </script>
 </body>