Version 3 server won't start if --log included

Hello,

When I try to start the server:
"C:\Program Files\Calibre2\calibre-server.exe" --port 8888 --log C:\Users\Administrator\Documents "E:\Dropbox\Calibre Lib"

it says:Python function terminated unexpectedly
[Error 5] CreateFileW: Access is denied. (Error Code: 1)
Traceback (most recent call last):
File "site.py", line 101, in main
File "site.py", line 78, in run_entry_point
File "site-packages\calibre\srv\standalone.py", line 193, in main
File "site-packages\calibre\srv\standalone.py", line 63, in __init__
File "site-packages\calibre\srv\utils.py", line 384, in __init__
File "site-packages\calibre\srv\utils.py", line 330, in __init__
File "site-packages\calibre\srv\utils.py", line 333, in set_output
File "site-packages\calibre\utils\shared_file.py", line 168, in share_open
File "site-packages\calibre\utils\shared_file.py", line 161, in os_open
File "site-packages\calibre\utils\shared_file.py", line 159, in os_open
WindowsError: [Error 5] CreateFileW: Access is denied.

If I omit the log option it runs fine. I am in the Administrator account when running this so I should have permission to my own Documents folder.

I've tried with and without a file name even though the doc page says directory but that made no difference.

Is this a bug, or just another thing my limited mind-reading ability has prevented from figuring out?