Routing fails if parameters contains slash

Hi,
I see this was reported a while back and resolved, but i cannot find the resolution.

I need to be able to pass slashes in the final segment of my route:

i.e for a department called 'A/P'for i want to be able

https://somefunction/api/departments/A%2FP

I set up my route like this:
Route = "departments/{dept}"

it works fine if there are no slashes (encoded as %2F) in the department, but if there is a slash it returns a 404.

How can I fix this?