Hot to pass a default parameter for std::shared_ptr

This question already has an answer here:

• Can virtual functions have default parameters? 5 answers

I have a function of type

virtual void foo(bla, bla, bla, std::shared_ptr<LoggerInterface> logger) = 0;

And I want to pass a default parameter with NULL pointer, something like:

virtual void foo(bla, bla, bla, std::shared_ptr<LoggerInterface> logger = NULL) = 0;

So that in implementation, if logger is NULL I do nothing with it, otherwise I use the logger.

I've tried to look for a solution but cannot find..