The invention provides an injectable dermal filler composition comprising crosslinked hyaluronic acid and/or a pharmaceutically acceptable salt thereof (HA), and a vitamin C derivative covalently conjugated to the crosslinked HA, the vitamin C derivative being selected from ascorbic acid 2-glucoside (AA2G), sodium ascorbyl phosphate (AA2P) and ascorbyl 3-aminopropyl phosphate (Vitagen).