New cinema displays' power button

On the old 23" cinema display, the power button would put the computer to sleep or wake it, depending on its current state. On the new 23" cinema display, the power button brings up a dialog asking "Are you sure you want to shut down your computer now?"

No, I'm sure I don't. I want to put it to sleep, like before. Having to click the "Sleep" button sucks ("Shut Down" is the default). I've looked in System Preferences, but the Options tab in the Displays item has the "Puts the system to sleep or wakes it" option selected. I don't want "Turns the display on and off" or "Does nothing". I want what I seem to have selected.

Only that's not what I get, and I don't understand why.