Initial integrator states in MPC toolbox.

To guarantee offset free control the MPC toolbox adds an integrator for each measurment in your system model. The particular model I am working with is a "delta" model, that is it shows the changes from some steady-state condtion. I would like to use the integrator in the model to take care of that steady-state condition rather than always subtracting a bias from measurement and setpiont. To do this I would have to initialize the integrator to a non-zero value. For the actual model states I use:

MPCobj.Plant = [...]

but how do I initialize the disturbance integrator?

Thanks, mike