How can I stop the password field being pre-populated on edit?

Set autocomplete="off" in the form and the input tags

<form name="blah" autocomplete="off">
<input type="password" autocomplete="off">
</form>

The line f.password_field :password, :value => '' didn't work for me (on rails 3.1). Although I coud empty the field with f.password_field :password, :value => nil.

Regards