Why do I get this error saying I am not initializing a const?

I have specified a value for the const member variable, check the constructor initialization list.

I have always initialized const variables this way and it worked. What I am asking is not some way to circumvent the problem but why it doesn’t work here. Is it a matter of C++11 or some kind of unreal issue?

Two sources that show how to initialize const variables in c++ the way I did it: