The Gravecrawler and the Vampire

[Fuzzball]

One of the PCs in my current campaign is a vampire. One option for a source of information for my players is a gravecrawler (MMII p118). I’m not sure how the gravecrawler’s Calcifying Aura should effect an undead though.

The presence of a gravecrawler is enough to cause flesh (living of dead) to harden and calcify, turning slowly into stone…Every creature within the area must make a Fortitude save (DC 22) each round or take 1d2 points of Constitution damage…

On the one hand, undead are immune to ability damage, and they don’t have a Constitution score to begin with. On the other, the effect is more of a transmutation than anything else and the entry says that gravecrawlers are immune to their own aura and the auras from others of their kind.

So, the calcifying aura really ought to affect undead. I’m just not sure how to implement it. Any suggestions out there?

[ScS of the Fraternity]

Frankly, the rules don't seem to back up the use of this ability against undead. Con damage is Con damage.
I suppose you could rule that aginst undead it drains the Dex score - leaving undead "alive" but frozen in place.