Remove runtime defined user

Hello,

How can I remove runtime defined user from my task.

I tried it in a BCO with the GP API:

IGPProcessRoleInstance processRoleInstance = executionContext.getProcessRoleInstance();

processRoleInstance.removeUser(myUser);

I also tried the removeRuntimeDefinedUser()-Method, but it doesn’t work either. (had no exceptions). Anyone an idea how to remove one of my users?

Regards Robert