function bp_add_template_stack_locations( $stacks = array() ) {
	$retval = array();

	// Get alternate locations.
	$locations = bp_get_template_locations();

	// Loop through locations and stacks and combine.
	foreach ( (array) $stacks as $stack ) {
		foreach ( (array) $locations as $custom_location ) {
			$retval[] = untrailingslashit( trailingslashit( $stack ) . $custom_location );
		}
	}

	/**
	 * Filters the template locations to template files being searched for.
	 *
	 * @since 1.7.0
	 *
	 * @param array $value  Array of all template locations registered so far.
	 * @param array $stacks Array of template locations.
	 */
	return apply_filters( 'bp_add_template_stack_locations', array_unique( $retval ), $stacks );
}