Particle Info Index lost with children


I just made a simple test, a plane that emits 9 cubes.
In cycles I used a material for the cube, so depending on Particle Info/index number the cube will be red, blue or green (using modulo function).
Work OK, see the blend file joined.
But when I use Children option, all the cube are red (=0 for Particle Info / index)
I think they would inherit the Particle Info / index of the parent. Is it a bug ?
I use blender 2.68a on linux 64.

Attachments (85.2 KB)