Change TextField passwordMask dynamically

I'm trying change the TextField passwordMask attribute dynamically, but it works only one time (from true to false).

".password": {
    passwordMask:true
}

<TextField id="passwordSignup" class="password" hintText='Password' />

if($.passwordSignup.passwordMask == true) {
   $.passwordSignup.setPasswordMask(false);
} else {
   $.passwordSignup.setPasswordMask(true);
}

Application Type: Mobile Platform & version: iOS 6.1 Device: iOS simulator Titanium SDK: 3.1.1.GA