IObjectClassEvents_Event not firing events on Undo?

Hi,
In our .NET (C#) ArcMap extension, we are successfully listening to Create/Change/Delete events on a feature class (well, a Table). However, we just realized that an Undo does not trigger the corresponding event.
So basically, if a user edits a row, we get the changed information properly. But then, if they undo their change (Ctrl+Z), we don't get a second event with the appropriate record. This causes our data to be out-of-sync.

What are we missing?

Regards,

Eric.