odd completion misbehavior?

[Danek Duvall <duvall@xxxxxxxxxxxxxx>]

With the following completion function:

	_danek() {
		_arguments \
			"--zoo-name" \
			"--zipple-zoo-name"
	}

and running under zsh -f with only

    autoload -Uz compinit
    compinit -i
    compdef _danek danek

if I type "danek --z<TAB>", I end up with "danek --z-name", with the cursor
on the dash between "z" and "name".  If I hit tab again, I end up with
"danek --zoo-name ", with the cursor after the final space.  If I setopt
menucomplete, I get reasonable behavior.

What have I done wrong with the completion function?

Thanks,
Danek