stty -echo doesn't work?

apologies if this has been posted before.

I just noticed that the following command

	$ stty -echo

does not work in an interactive dash(1) shell.
Initially I thought it was an issue with my terminal
but I tried in bash(1) as well and it works fine.

If this is a known issue and there is some work
around (i.e., I'm doing something wrong?), I'd love
to know how to fix it, but if it is a genuine bug I
will take a look and send a patch if/when I fix it
:)

Thanks!
-- 
S.