how do i stop from getting doughnut shaped shadows on background from beauty dish?

[Phtoo]

how do i stop from getting doughnut shaped shadows on background from beauty dish? - using mola setti white with sock.

 

[Derrel]

Stop using it so close to the backdrop.

 

[Phtoo]

how far from the backdrop would be standard?

 

[Big Mike]

Or light the background so that shadows aren't visible on it.

It would really help if you could show us some examples and let us in on your setup.