Hybrid position/force control enables a robot to apply specified forces to a constraint while moving along a prescribed path. Stability analyses of hybrid-controlled robots typically assume that the robot is always in contact with the constraint. Yet in most practical applications, the end effector is not initially in contact with the constraint and can lose contact during the task. Constraints of this type are called unilateral constraints and have received relatively little attention in the robotics literature. In the present note, we examine the stability of a multi-degree-of-freedom robot in contact with a unilateral constraint and take elastic deformation of the constraint into account. It is shown that with a continuous hybrid control applied, the system is globally asymptotically stable and achieves zero steady-state position and force error. The hybrid control requires no knowledge of the manipulator dynamic parameters or the stiffness/position of the constraint.