Invalid app store icon: it contains transparency when it shouldn't

Hi,

I am trying to validate my app and I get the error:


Invalid App Store Icon. The App Store Icon in the asset catalog in 'my_app_name.app' can't be transparent nor contain an alpha channel.


What I've tried is open the App-1024x1024@1x.png file and export it unchecking the alpha tick.

Indeed right now I can see the white parts of the image in Xcode image preview (I do not see the transparency).


P.S. the other images of the app do contain alpha. Do I have to remove alpha from all images?