diff --git a/src/wp-includes/class-walker-page.php b/src/wp-includes/class-walker-page.php
index 8bec66f..2418a67 100644
--- a/src/wp-includes/class-walker-page.php
+++ b/src/wp-includes/class-walker-page.php
@@ -61,7 +61,23 @@ class Walker_Page extends Walker {
 			$n = '';
 		}
 		$indent = str_repeat( $t, $depth );
-		$output .= "{$n}{$indent}<ul class='children'>{$n}";
+
+		// Default CSS class.
+		$classes = array( 'children' );
+
+		/**
+		 * Filters the CSS class(es) applied to a page children list element.
+		 *
+		 * @since 4.8.0
+		 *
+		 * @param array $classes The CSS classes that are applied to the menu `<ul>` element.
+		 * @param array $args    Arguments for outputting the next level.
+		 * @param int   $depth   Depth of page. Used for padding.
+		 */
+		$class_names = join( ' ', apply_filters( 'page_children_list_css_class', $classes, $args, $depth ) );
+		$class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';
+
+		$output .= "{$n}{$indent}<ul {$class_names}>{$n}";
 	}
 
 	/**