subst command replaces existing drives (bug)

Hi!

Testing 70319 reactos version, i see that subst command (command line) work now, great, but i see an error. If execute the subst command and the letter (subst transform a path in virtual drive) exists already reactos reemplace the drive with the new drive (path), this is a bug because should show an error "the drive is in use already or similar" and not set the new drive, because exists in the system.
On Windows this work very good, but in reactos exists this problem, i attach a two screenshots with the problem, greetings.