Gov. Code, § 5105

Whenever by operation of law or by order the bonded indebtedness of any issuing body is reduced in amount, the interest thereon reduced, the time for the payment thereof or of any tax or assessment levied to pay the indebtedness, the interest thereon, or any portion of both or either of them, extended, or any other term or condition for the payment thereof altered, the obligations of all guarantors are reduced as to principal and interest, or either of them, extended as to the time of payment and altered as to any and all terms thereof in the same manner and to the same extent as the obligation or obligations of the issuing body and the tax or assessment payers, or either of them, are reduced, extended or altered.