does c2d support sytems with uncertainty?

Hello, I have a system with uncentainty, when I apply the c2d command I get the following error:

"Error using DynamicSystem/c2d (line 100) The "c2d" command cannot be used for models of class "uss"."

Is this normal? If so, how can I discretize systems with uncertainty?

I'm running Matlab R2015a, we have the Robust Control Toolbox at our institution

Thanks for your help.