Postprocessing weird rendering in outer regions

Hi, I’m using Unity 2020.2.5f1. I have a scene in which I drop some cubes on a plane with some other simple geometric shapes. I use postprocessing to mimic fisheye distortion. My problem is that the cubes that are outside the region of the camera without the postprocessing effect are rendered weirdly when I turn on the postprocessing.




Does anybody have any idea how to fix this?

Thanks in advance.