Tramp + ido-mode: error with "/su:"

[Teemu Likonen]

I get annoying error when using Tramp and ido-mode together and try to
edit file through /su or /sudo. I do C-x C-f (ido-find-file), type
"/su:" and just after entering the colon a new window named *tramp/scp
su* pops up with the text:

    ssh: Could not resolve hostname su: Name or service not known

    Process *tramp/scp su* exited abnormally with code 255

I can continue typing the path (like /su::/etc/foo) without further
problems and Tramp and Ido completion work nicely. It's the opening of
new window which I'd very much like to get rid of. With Ido mode turned
off there are no errors.

Is it possible to fix this issue somehow?