OR matcher no longer accepts null example value

[topr]

On the 3.x Pacts DSL version I used to have a contract defined like

{
    errorCode or(failureCode, nonEmptyString(), nullValue())
}

...where the failureCode variable was either populated or null depending on the test case variant executed.
The nonEmptyString() is my custom method based returning configured regex matcher (irrelevant to the issue).

I've just updated to the 4.1.x Pact libs and the or() matcher throws IllegalArgumentException when the example value is null.

What is the way now to declare a contract which says: expect some value of certain format or null?

[topr]

I've used version 4.1.14 and the issue is gone. Thanks!