This decision holds that the trial court erred in granting one defendants summary judgment based on plaintiff’s failure to timely file a government claim. Plaintiff alleged facts giving supporting its arguments that the defendant had expressly and impliedly waived the government claims defense. The fact that plaintiff filed a late government claim did not defeat the implied waiver argument since waiver, unlike estoppel, is based on the defendant’s voluntary relinquishment of the limitations defense, not requiring any proof that the plaintiff was misled or prejudiced thereby. The express waiver argument was based on statements by the defendant’s litigation counsel during pre-suit negotiations. Plaintiff’s evidence raised a triable issue as to the attorney’s apparent authority to act for the defendant in that regard. Moreover, Gov. Code 930.4 provides that a government claim need not be filed if the parties have contractually agreed to a different dispute resolution procedure. Here, the parties did. Although the agreement was later ruled void under Gov. Code 1090, its dispute resolution procedure survived.