An indirect firing fastening tool with an anti-firing trigger support. The tool comprises, in one case, an axially movable equipment with a tip guide projecting from the case to drive a fastening member into a support material, a reception housing for a fastener charger and anti-firing safety means to prevent the recoil of the tip guide. Advantageously, an anti-firing trigger support is mounted on said reception housing to convert the tool into a mono-firing tool, the trigger being arranged to cooperate with the anti-firing safety means so as to remove them and authorize firing.