guam (0.9.4) crash after update

[JP Horst]

After updating Kolab16 (on Centos7) yesterday and again this morning.  
IMAP is not accessible presumably because guam doesn't start due to a  
crash.

In messages ist says:
guam: /usr/lib64/erlang/lib/kolab_guam-0.9.4/bin/guam: line 25: which:  
command not found

Using the new /etc/guam/sys.config or rerunning setup-kolab guam does  
not change this.

Does anyone know how to solve this problem?

Thanx
JP