You could try: "Constraint: The value that my current utility function would assign to the universe after this wish is implemented must be higher than the value my current utility function would assign to the universe that would have existed had you not implemented this wish."

... Which probably causes the Genie to, at best, throw an undefined-error, since human beings don't have well-defined utility functions. Since it's malicious, it will probably search through all of your desires, pick one of them at random to count as "my utility function", and then reinterpret the body of the wish to maximise that one thing at the expense of all others.