A square tool holder (10) for an impact wrench is provided, including an anvil (1), on which a drive square (2) is situated for accommodating a tool, in particular an impact wrench socket, and including a safety bolt (3) for securing the accommodated tool, the safety bolt (3) being spring-mounted in the drive square (2) in such a way that the safety bolt is movable perpendicularly to the axis of rotation (D) of the anvil (1), the safety bolt (3) having a rounded, preferably hemispherical surface (3′), which protrudes from a holding surface (2′) of the drive square (2) in a state of spring-extension (AZ) of the safety bolt (3) and is at least partially countersunk in the holding surface (2′) in a state of spring-compression of the safety bolt (3), the safety bolt (3) being secured against falling out by at least one safety pin (4, 4′) situated in the drive square (2).