Example

class Base {
public:
virtual void fnc(int param = 0);
};

class Derived: public Base {
public:
void fnc(int param = 1){}
};

Solution

Do not redefine a new default value in the base class. Since non-virtual functions should not be overrided, making a non-virtual interface indicates that the default parameter should not be changed.

class Base {
public:
void fnc(int param = 0){
fncWork(param);
}

private:
virtual void fncWork(int param);
};

class Derived: public Base {
private:
virtual void fncWork(int param){}
};