[Apache2.4] modified VirtualHost File on default after restarting Apache

Hey everybody,

I just set up a new nextcloud. I’m using Nextcoud 12, PHP 5.6 and Apache 2.4.

On the Admin Settings page I get the following error:

The “Strict-Transport-Security” HTTP header is not configured to at least “15552000” seconds. For enhanced security we recommend enabling HSTS as described in our [security tips].

As it is written there I have to change my Apache VirtualHost File and add the mod-headers.c module.

I did so, but after restarting my server the VirtualHost File is back to default without keeping the new module.

Does anyone know why that happends?