Using 'override' for a function that has been declared using 'typedef'

C++ 11 introduce the 'override' specifier for a function and I find it useful as it makes it explicit that a virtual function is being overridden. However, I can't seem to get it work for a function that has been declared using a typedef.

I understand that 'override' is not a keyword, has it got something to do with that?

The following code illustrates my point:

#include <iostream>

typedef char ReturnsChar();

class Basic
{
    public:
    virtual char get_a();
    virtual ReturnsChar get_z;
};

char Basic::get_a() { return 'a'; }
char Basic::get_z() { return 'z'; }

class Capitalized : public Basic
{
    public:
    // Can override explicitly if I use the normal definition
    char get_a() override;

    // Compiles if I use the typedef but not 'override'
    ReturnsChar get_z;

    // Will not compile, but would like to do this
    //ReturnsChar get_z override; 

};

char Capitalized::get_a() { return 'A'; }
char Capitalized::get_z() { return 'Z'; }

int main()
{
    Basic foo;
    Capitalized bar;

    std::cout << foo.get_a() << std::endl; // a
    std::cout << foo.get_z() << std::endl; // z
    std::cout << bar.get_a() << std::endl; // A
    std::cout << bar.get_z() << std::endl; // Z
}

I'm using GNU's g++ 8.2.0 and the error it gives me is

error: expected ';' at end of member declaration
ReturnsChar get_z override;
            ^~~~~
                      ;
error: ‘override’ does not name a type; did you mean ‘ctermid’?
     ReturnsChar get_z override;
                       ^~~~~~~~
                       ctermid