[bug] negative modifiers lost after loading

While playing with some modding stuff I stumbled over an odd behaviour:
Whenever I load a saved game all negative modifiers to an attribute are lost. In the XML of the savegame file the changes appear, but after laoding and saving again they are lost.
I don’t know if this has any influence on the unmodded game, as most of the attribute changes degrade pretty soon anyway.
But I thought I should mention this anyway.