A catheter hub assembly. The catheter hub assembly includes a catheter hub body, a septum and a septum retainer, the catheter hub body having a distal end, a proximal and an internal wall defining an internal fluid passageway therebetween, the internal wall defining a transitional step within the internal fluid passageway, the septum positioned within the internal fluid passageway such that a distal end of the septum abuts up against the transitional step, the septum retainer at least partially receivable within the internal fluid passageway and having an outer wall shaped and sized to interlock with the inner wall of the catheter hub body, the outer wall including one or more lateral ribs configured to inhibit rotation of the septum retainer relative to the catheter hub body.
