whitespace.el change in emacs 23.3 on F16?

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Just upgraded from F13 to F16 which means Emacs has been bumped from 23.2 to 23.3.

I have global whitespace mode enabled, and have it highlighting all spaces. This is bearable because I cutomsed the font to be only slightly different than the background.

On this slightly newer emacs however all spaces are being shown in bright white dots, not the subtle grey I have configured.

I've run describe-face whitespace-space and indeed my customisation is being picked up - emacs thinks it should be light grey. I looked at whitespace.el and whitespace-space seems to still be the cutom face used for spaces.

What could have changed here and how do I get back my subtle space hilighting?