diff --git a/vendor/box2d/box2d.odin b/vendor/box2d/box2d.odin
index 640f430b8..8b0a57a4e 100644
--- a/vendor/box2d/box2d.odin
+++ b/vendor/box2d/box2d.odin
@@ -1370,7 +1370,7 @@ foreign lib {
 
 	// Create a motor joint
 	//	@see b2MotorJointDef for details
-	CreateMotorJoint               :: proc(worldId: WorldId, def: MotorJointDef) -> JointId ---
+	CreateMotorJoint               :: proc(worldId: WorldId, #by_ptr def: MotorJointDef) -> JointId ---
 
 	// Set the motor joint linear offset target
 	MotorJoint_SetLinearOffset     :: proc(jointId: JointId, linearOffset: Vec2) ---