Hi, I have exposed a bigint class which has no constructor for long_ . I added an additional constructor by defining .def("__init__", make_constructor(bigint_constructor)) This works fine. Now I want to use the implicitly_convertible function which expects from the class to have an constructor which takes the first argumen (in this case a long_) I used implicitly_convertible but now the problem is that the original c++ class has no such constructor, but the wrapped class. How can I make him use my new constructor in implicitly_convertible? Benjamin