An auto-injector for administering a dose of a liquid medicament (M) is presented having an elongate case arranged to be held by a user, a tubular chassis telescoped in the case and biased against the case so as to protrude from the case. The injector also includes 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. A trigger button is distally arranged in or on the case, wherein the trigger button is initially coupled to the case in a manner to protrude distally from the case and interlocked to the chassis in a manner preventing the trigger button from disengaging the case.