= false ) {
	/*
	 * Account for the filter being called without the $args or $depth parameters.
	 *
	 * This occurs when a theme uses a custom walker calling the `nav_menu_css_class`
	 * filter using the legacy formats prior to the introduction of the $args and
	 * $depth parameters.
	 *
	 * As both of these parameters are required for this function to determine
	 * both the current and maximum depth of the menu tree, the function does not
	 * attempt to remove the `menu-item-has-children` class if these parameters
	 * are not set.
	 */
	if ( false === $depth || false === $args ) {
		return $classes;
	}

	// Max-depth is 1-based.
	$max_depth = isset( $args->depth ) ? (int) $args->depth : 0;
	// Depth is 0-based so needs to be increased by one.
	$depth = $depth + 1;

	// Complete menu tree is displayed.
	if ( 0 === $max_depth ) {
		return $classes;
	}

	/*
	 * Remove the `menu-item-has-children` class from bottom level menu items.
	 * -1 is used to display all menu items in one level so the class should
	 * be removed from all menu items.
	 */
	if ( -1 === $max_depth || $depth >= $max_depth ) {
		$classes = array_diff( $classes, array( 'menu-item-has-children' ) );
	}

	return $classes;
}