SkyboxImage projects white square instead of texture

I’m trying to project a moon texture onto the skysphere using the SkyboxImage function in the Material Panningclouds that is used for the skymaterial. I use the XVector of the directional light that serves as the moon light just like it is done for the sun. Then I use the mask output and add it just like the sun.

However I only get white squares that are not in the correct position.

I also tried making a moon with the sphere mask just like the sun and it worked fine. But I want moon texture of course.

How do I use the SkyboxImage function properly?