GPU particles disappears when scaled at -1

Hello everybody !

Here’s my problem : My martian guy has 2 arms with big gun on it.
When he use them, I attach (through anim notify) a particle system to figure the muzzle flash.

Both arm are attach to a socket. One of these socket (the left one) has a scale set to -1 to make the right arm model the left one (simple symmetry)
Every things are fine except for one detail.
In my particle system, I’ve got some sparks that are GPU particle (with collision).

This specific emitter is not show on the left arm (the scaled one).


I try to make the material of the particle 2 sided but it doesn’t help…

How can I fix this ?