A wearable infusion device delivers a liquid medicant to a patient. The infusion device comprises a reservoir arranged to contain a liquid medicant to be delivered beneath a patient's skin. The reservoir has an outlet through which the medicant flows and a shape that forms at least one pocket that traps air isolated from the outlet. The infusion device further includes a conduit communicating with the outlet of the reservoir, and a pump that causes the medicant to flow from the reservoir into the conduit.