2 normal bump mapping doesn't mix

[Jean-Sebastien Perron]

I have a dirt shader + texture with a += BumpNormal(texture).
Also a stripe shader + texture with a += BumpNormal(texture).

Object
    mymodel
    spheremapping(dirt)
    planarmapping(stripes)

It does not work. What am I doing wrong?

Jean-Sebastien Perron
www.NeuroWorld.ws