Size in create animations api seems not to be working?

Hi!
I'm trying to create a 1024 by 1024 px animation adding this to my body, in POST to /animations:
"face": {
"top_left": [
0,
0
],
"size": 1024
}

the generated video, though, is always 512 by 512, instead.
The only other field in the request is the image path, that is already a 1024 by 1024 png image.

Thanks for any help.