restriction contract groovy script

I have this code on the Restriction of the Contract

boolean validCuit = true;
    proveedorInput.each { prov ->
        validCuit = validCuit && AltaProveedores.validarCuit(prov.cuit);
    }
    return validCuit;

I'm getting the following exception:

depends on cuit is neither defined in the script nor in dependencies.

**cuit **is a property that is defined as a field of proveedorInput. What I'm missing here?