Can not enable NSZombieEnabled ^^;;;

Question

I am using xcode_3.2.3_and_ios_sdk_4.0.1 and I setup everything the below.

To enable it (in xcode) 1. Double-click an executable in the Executables group of your Xcode project. 2. Click the Arguments tab. 3. In the “Variables to be set in the environment:” section, make a variable called “NSZombieEnabled” and set its value to “YES”.

But I can not see the NSZombieEnabled in Leaks. When I click X button on the right of Allocations, I only see the 4 items, not 5 items. I can not see "Enable NSZombie detection" check box.

My test iphone is 3G, updated 4.0 iOS. Could I use a device for using NSZombieEnable?

Thanks.