Blender scaling Bug (stl 3d printing)

I’m using blender a lot lately for rapid prototyping.
Some of the models get printed on a 3d printer.
Because I draw small parts I need the world scale to be in millimeters.
Each time I export to STL someone has to rescale the model up, a factor 1000.
So are my world settings wrong, or is this some bug ?.

Capture