A gas generant composition for an automotive inflatable restraint system is provided with a fuel having a thermally stable crystalline hydrate compound with a water release temperature of greater than or equal to about 140° C. The thermally stable crystalline hydrate compound serves as a ballistic modifier, which can serve to increase burn rate, reduce pressure sensitivity, reduce temperature sensitivity, and the like. The thermally stable crystalline hydrate compound may be selected from the group consisting of: a copper phthalate hydrate, copper pyromellitate dihydrate, copper fumarate dihydrate, copper (3-nitrophthalate) dihydrate, and combinations thereof.