It has been repeatedly decided that the officers of a mutual insurance company have no power to waive express stipulations of their policies or by-laws, which relate to the substance of the contract, although they may waive such as relate merely to the proof of loss. Priest v. Citizens’ Ins. Co. 3 Allen, 602. Buffum v. Fayette Ins. Co. Ib. 360. Abbott v. Shawmut Ins. Co. Ib. 213. Mulrey v. Shawmut Ins. Co. 4 Allen, 116. Brewer v. Chelsea Ins. Co. 14 Gray, 203. The present case falls within this principle. The defendants had, by a formal vote, prescribed the form in which their policies should be made. They had thus deliberately determined the liability which they were willing to assume; and their officers could not, without a violation of duty, have undertaken to bind them by a policy issued in a different form. But the plaintiff’s policy was in strict conformity to the prescribed form. She had distinct notice of the conditions on which she could with safety make alterations in her dwelling-house. And she proceeded to make such alterations, knowing that she had not complied literally with these conditions. We cannot say that a mutual insurance company, which wishes to prevent the possibility of controversy as to the terms of supplementary agreements, may not provide that it will not be bound by any oral consent, which its officers may give, to a variation in the terms of the liability which it has assumed. This is what the present company has undertaken to do. And although the case, upon the agreed facts, is one of hardship to the plaintiff, the rule of law cannot be varied on that account. And the receiver had no right to dispense with these rules, and determine the case upon principles of equity. See Worcester Bank v. Hartford Ins. Co. 11 Cush. 265. Pendar v. American Ins. Co. 12 Cush. 469. Loring v. Manufacturers’ Ins. Co. 8 Gray, 28.