[systemd-devel] problem apache2 service

[Nico - Clicom snc - www.clicom.it]

I have this error on my nas:
-- Unit apache2-safe.service has begun starting up.
Jan 12 08:55:47 ReadyNESSY systemd[5020]: apache2-safe.service: Failed 
at step EXEC spawning /usr/sbin/apache2: No such file or directory
-- Subject: Process /usr/sbin/apache2 could not be executed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- The process /usr/sbin/apache2 could not be executed and failed.

/usr/sbin/apache2 is a link:

root at ReadyNESSY:~# ls -l /usr/sbin/apache2
lrwxrwxrwx 1 root root 33 Sep 23 20:53 /usr/sbin/apache2 -> 
../lib/apache2/mpm-worker/apache2


How i resolve?

thanks
Nico