Bug using "-" last in `skip-chars-forward'

The following bug exists both in Emacs 21.3 and XEmacs 21.4 (patch 14): 1. Start (X)Emacs with -q -no-site-file. 2. Create a buffer and type "-" in it. 3. Go back to the beginning of the buffer. 4. Evaluate (skip-chars-forward "y-"). The point does not move, whereas I expected it to skip forward past the "-". That since a "-" last in a normal regexp character alternative is not special. `skip-chars-forward' does not use quite the same syntax, but according to the manual that detail should still be the same. Furthermore, if "-" in the buffer is replaced with "y", it still doesn't skip forward past it. I.e. when the string to `skip-chars-forward' or `skip-chars-backward' ends with a "-" that doesn't also start it, both it and the preceding character are ignored.