Backup in xampp fails with error “Call to undefined function posix_getpgid()”

I’m running Total Upkeep Version 1.14.13 on an xampp installation on Windows 10. When I try to do a backup I get this error message:

Fatal error: Uncaught Error: Call to undefined function posix_getpgid() in [Path]\wp-content\plugins\boldgrid-backup\admin\class-boldgrid-backup-admin-test.php:529 Stack trace: #0 [Path]\wp-content\plugins\boldgrid-backup\admin\class-boldgrid-backup-admin-in-progress.php(403): Boldgrid_Backup_Admin_Test::is_getpgid_supported() #1 [Path]\wp-content\plugins\boldgrid-backup\admin\class-boldgrid-backup-admin-in-progress.php(354): Boldgrid_Backup_Admin_In_Progress::is_running() #2 [Path]\wp-content\plugins\boldgrid-backup\admin\class-boldgrid-backup-admin.php(133): Boldgrid_Backup_Admin_In_Progress::is_done() #3 [Path]\wp-includes\class-wp-hook.php(303): Boldgrid_Backup_Admin->enqueue_styles('toplevel_page_b...') #4 [Path]\wp-includes\class-wp-hook.php(327): WP_Hook->apply_filters(NULL, Array) #5 [Path]\wp-includes\plugin.php(470): WP_Hook->do_action(Array) #6 [Path]\wp-admin\admin-header.php(102): do_action('admin_enqueue_s...', 't in [Path]\wp-content\plugins\boldgrid-backup\admin\class-boldgrid-backup-admin-test.php on line 529

Line 529 contains this code:

self::$is_getpgid_supported = false !== posix_getpgid( $pid );

When I insert the line “return false;” directly above that line, the backup appears to work correctly and there is no error message.