An internal combustion engine system (10) comprising a reductant delivery system (30) in reductant supplying communication with combustion exhaust, the reductant delivery system (30) comprisinga reductant tank (32) containing reductant, a doser (36) that supplies reductant to the combustion exhaust, a reductant pump (34) that draws reductant from the reductant tank (32) and delivers the reductant to the doser (36), a filter module (100) positioned within the reductant tank (32) to filter the reductant, the filter module (100) comprising a venting port (210) positioned to release entrained gas from the filter module (100) to restrict entry of entrained gas into the reductant pump (34) and a venting line (102). The filter module (100) is positioned adjacent to a bottom wall of the reductant tank (32) and the venting line (102) extends substantially vertically to convey the gas from the venting port (210) through the reductant in the reductant tank (32) to a gas reservoir above the reductant within the reductant tank (32).