diff --git a/res/css/views/messages/_MessageActionBar.scss b/res/css/views/messages/_MessageActionBar.scss
index 05887eea3e..685c2bb018 100644
--- a/res/css/views/messages/_MessageActionBar.scss
+++ b/res/css/views/messages/_MessageActionBar.scss
@@ -26,6 +26,7 @@ limitations under the License.
     top: -18px;
     right: 8px;
     user-select: none;
+    // Ensure the action bar appears above over things, like the read marker.
     z-index: 1;
 
     > * {