Can't set Breakpoint within an os_activity_initiate block

I'm just starting out trying to use os_activity and have hit an annoyance. Attempting to add a breakpoint to any line of code with os_activity_initiate block does not work as expected. Instead it seems to break after the call to os_activity_initiate.

E.g Consider this:

- (IBAction)doActivity:(id)sender
{
    os_activity_initiate("Test Activity", OS_ACTIVITY_FLAG_DEFAULT, ^{
        NSLog(@"Doing activity");
        NSBeep(); // <<-- Try to add a preakpoint here
        NSLog(@"Finished activity");
    });
}

Try to put a breakpoint at the NSBeep() line. By the time it fires, both NSLog calls will have already been done.

Only solution I can find is to wrap all such code inside os_activity_initiate blocks into a local block (or other function) but that's no fun.

BTW - Xcode 9.2 Debug configuration and macOS 10.13.2