9. A husband married after the thirty-first day of December, 1865, shall not by reason only of such marriage be liable to the debts of his wife contracted before marriage, but the wife shall be liable to be sued for, and shall, to the extent of her separate property, be liable to satisfy such debts as if she had continued unmarried: Provided that nothing contained in this section shall invalidate any contract into which a husband may, before the passing of this Act, have entered in consideration of his wife's antenuptial debts.