JESS: nil equality checking

[Velagapudi_Vidya]

I have a small example as follows

 

(deftemplate Customer (slot surname) (slot givenname))

 

(defrule validateCustomerRule

    ?c <- (Customer {surname == nil || givenname == nil})

    =>

    (assert (invalidCustomer ?c))

    )

 

(assert (Customer (surname nil) (givenname brady)))

 

(run)

(facts)

 

 

When I run this, I expect invalidCustomer to be  asserted but instead

I am only getting the customer fact

 

f-0   (MAIN::Customer (surname nil) (givenname brady))

For a total of 1 facts in module MAIN.

 

Am I missing something?

 

I am using jess70.