Cannot register new custom function

[Aleksa-Amp]

I am trying to register new custom expression function:

return new DocxStamperConfiguration()
            .exposeInterfaceToExpressionLanguage(TestFunction.class, new TestFunctionImpl())
            .build();

public interface TestFunction{
        void test();
    }

    public static class TestFunctionImpl implements TestFunction{
        @Override
        public void test() {
            System.out.println("Test");
        }
    }

But once I try to process document I get the following error:

IllegalArgumentException: object is not an instance of declaring class

This is the expression in my docx file: ${test()}.
How can I solve this problem?

[caring-coder]

Works without issues in current version of our fork office-stamper