Import layout from 1.8 into 4.0


we’ve setup a new xibo cms (docker), version 4.0.6 and are trying to import the layouts from our old 1.8.9 CMS.
But we get the next error when we import into de 4 version:

Unsupported format. Missing Layout definitions from layout.json file in the archive.

How do we work around this without having to recreate all our layouts?