Friend function error: member is inaccessible

[bool maybe]

This is the part of the program that's giving me trouble:

class Money
{
public:
	friend Money operator +(const Money& amount1, const Money& amount2);
	friend Money operator -(const Money& amount1, const Money& amount2);
	friend Money operator -(const Money& amount);
	friend Money operator ==(const Money& amount1, const Money& amount2);

	Money(long dollars, short cents);
	Money(long dollars);
	Money();

	double get_value() const;
	friend istream& operator >>(istream& ins, Money& amount);
	friend ostream& operator <<(ostream& outs, Money& amount);

private:
	long all_cents;
};
//main part of program goes here


ostream& operator <<(ostream& outs, const Money& amount)
{
	long positive_cents, dollars, cents;
	positive_cents = labs(amount.all_cents);
	dollars = positive_cents/100;
	cents = positive_cents%100;

	if(amount.all_cents < 0)
	{
		outs << "-";
	}
	outs << '$' << dollars << '.';

	if(cents < 10)
	{
		outs << '0';
	}
	outs << cents;

	return outs;
}

This program gives me an error described in the title. When I remove the "const" (line 23) it goes away. Does the problem go away after deleting "const" because the compiler is afraid that I may change the value of "amount.all_cents" or is this error the results of some other reason? Thanks.

[bool maybe]

And is there any way that I could keep the "const" part in the program?

[firedraco]

That's because your prototype in the class (line 15) is taking a non-const Money reference, unlike your definition.