Apache error when adding a new virtual server

webmin 1.340
usermin 1.270
virtualmin 3.39.gpl

When i add a new virtual server i receive the following error:

Adding Apache user apache to server's group ..
.. done

.. Apache website failed! : Undefined subroutine &main::save_domain_ruby_mode called at /usr/libexec/webmin/virtual-server/feature-web.pl line 1856.

when i check apache, the virtualhost is created and running, but when managing the virtual server "Web virtual server enabled?" is not checked. When i try to delete the server, everything is removed with exception of the the apache virtualhost, which has to be then manually removed.

The above error prevents virtualmin from "remembering" or "seeing" that the virtualhost exists. Thus it can not be managed.

Status: 
Closed (fixed)