A closure bolt for an injector of a modular common-rail fuel injection system includes at least one high-pressure port for high-pressure fuel and a bolt-like portion which is configured to be inserted into an opening of the injector and which has a first, preferably conical, sealing surface for closing the opening in a high-pressure-tight manner. The bolt-like portion has a high-pressure bore which is hydraulically connected to the high-pressure port and which issues into the injector. The closure bolt further includes a throughflow limiter configured to limit the flow rate of fuel delivered into the injector. The bolt-like portion has an insert in which the throughflow limiter is formed and which bears the first sealing surface.