Invisible mouse pointer in wayland (riverwm)

I installed Nixos on my laptop and river as a package through the configuration.nix.
Inside a river session i can use the mouse with the touchpad, except i cant see it.
I can just see the effect of hovering / clicking.

This seems to be no nix-os issue:

The strange thing is the same version worked on manjaro on the same hardware (pinebook-pro) with the same river-version…