Problem "Invalid default namespace ID detected"

[vbluis]

Hi, I have this problem when I install vaultwiki:

Only admins can see this error. Other users can visit the site normally, but your immediate attention is needed in the AdminCP.

Invalid default namespace ID detected. Make sure that you have set up the default namespace via the Namespace Manager. If you have, it is possible that the Namespace Cache is not up to date because of a recent change or VaultWiki upgrade. To solve this issue, simply go to the Namespace Manager and select [Rebuild All Namespaces].

If you still receive this error after rebuilding namespaces, contact VaultWiki support.

Thank you very much

[pegasus]

Make sure that you have completed this installation step: https://www.vaultwiki.org/manual/Initial-Setup

[vbluis]

Thank you