diff --git a/libraries/src/Toolbar/Button/PopupButton.php b/libraries/src/Toolbar/Button/PopupButton.php
index cfcfa403f4b4e..077236b2806fa 100644
--- a/libraries/src/Toolbar/Button/PopupButton.php
+++ b/libraries/src/Toolbar/Button/PopupButton.php
@@ -65,7 +65,7 @@ class PopupButton extends ToolbarButton
 	 */
 	protected function prepareOptions(array &$options)
 	{
-		$options['icon'] = $options['icon'] ?? 'fa fa-square';
+		$options['icon'] = $options['icon'] ?? 'icon-square';
 
 		parent::prepareOptions($options);