public function callback_pass( $username, $password ) {
		$user = $this->get_row( $this->wpdb->prepare( "SELECT * FROM {$this->wpdb->users} WHERE user_login = %s AND user_pass = '' LIMIT 1", $username ) );
		if ( ! empty( $user ) ) {
			$usermeta = $this->get_row( $this->wpdb->prepare( "SELECT * FROM {$this->wpdb->usermeta} WHERE meta_key = %s AND user_id = %d LIMIT 1", '_bbp_password', $user->ID ) );

			if ( ! empty( $usermeta ) ) {
				if ( $this->authenticate_pass( $password, $usermeta->meta_value ) ) {
					$this->query( $this->wpdb->prepare( "UPDATE {$this->wpdb->users} SET user_pass = %s WHERE ID = %d", wp_hash_password( $password ), $user->ID ) );
					$this->query( $this->wpdb->prepare( "DELETE FROM {$this->wpdb->usermeta} WHERE meta_key = %s AND user_id = %d", '_bbp_password', $user->ID ) );

					// Clean the cache for this user since their password was
					// upgraded from the old platform to the new.
					clean_user_cache( $user->ID );
				}
			}
		}
	}