Pass enum as function argument

This is a simplified example illustrating my problem. The following gives me the: error C2065: 'State' : undeclared identifier

myclass.h

class MyClass
{
    enum class State { IDLE, WALK_RIGHT, WALK_LEFT };
    void SetState(State);
}

myclass.cpp

#include "myclass.h"
void SetState(State state)
{
    //...
}

Any idea what's wrong here? Thanks in advance!