An interlock for a skid steer vehicle with a rear engine compartment and a rear door to that compartment includes a beam that is mounted transversely to the bottom of the door and has an upward facing surface that, like the beam, extends across the entire rear engine compartment opening. An interlocking second member is fixed to the chassis and extends across the rear engine compartment opening. When the door is impacted and forced upward, the first beam engages the second interlocking member over its width and transfers the force from the door (and beam) to the chassis When the door is impacted with a forward-directed force, the first beam also contacts the second member and transfers the forward forces through the second member to the chassis. Injury to the door is reduced or eliminated by transferring door impact forces to the chassis since the first beam extends substantially the entire distance across the door and is fixed to an inner surface of the door's frame.