Defocus Node

Why would the defocus node work in the backdrop preview of a node setup, but not when rendering with F12?

All I have is the defocus node in the node setup and yes, “use nodes” is checked. With backdrop checked, the model is out of focus where I want it to be but when it is rendered, everything stays in focus.

Is the output node connected to the defocus node

Usefull to see what you have

I appended it into another scene and it works. Must have been some operator error. Thanks for trying to help though.