An auto-injector for administering a dose of a liquid medicament includesan elongate case arranged to be held by a user,a tubular chassis telescopable in the case and biased against the case so as to protrude from the case,a syringe with a hollow injection needle, a drive spring and a plunger for forwarding load of the drive spring to a stopper of the syringe, anda trigger button which is initially abutted against the case thus preventing actuation.