const not enforced in definition of member function

I'm wondering why the following code compiles when the definition of the member function does not have the same signature as the declaration (definition is missing const).

#include <iostream>

class myClass {
public:
    void myFunc(const int);
};

void myClass::myFunc(int a){
    a += 1;
    std::cout << a << "\n";
}

int main()
{
  myClass myObject;
  myObject.myFunc(5);
}