Transparency of a resized keyed image

I am using a Qualifier node for quick green screen keying on the interview footage. Adding a background on a video track underneath poses no problem, I can see it instead of the green screen. However, upon attempting to crop or resize (smaller) the keyed interview, I encounter an unexpected outcome: instead of maintaining transparency, it seems like there is no alpha channel, resulting in black areas being added to the cropped region.

How can I fix this ?

Applying a power window to my whole green screen area solves the issue on the resize front, but not for cropping.

You need to connect the source to the mask input of the node.

Thank you!!!