A filling adapter (12) for connecting a syringe (14) containing an injection solution to an injection device (10), the filling adapter (12) comprises a hollow sleeve (16) and an adapter element (18) accommodated within the sleeve (16), wherein the adapter element (18) comprises a first connecting port (20) adapted to be connected to the syringe (14) and a second connecting port (22) adapted to be connected to the injection device (10), and wherein the adapter element (18) is provided with a through-opening (26) extending therethrough. A cannula (27) protrudes from the second connecting port (22) of the adapter element (18), wherein the cannula (27) is arranged in fluid communication with the through-opening (26) extending through the adapter element (18), and wherein the adapter element (18) further is provided with a venting device (64) which is adapted to vent gas introduced from the syringe (14) into the injection device (10) via the through-opening (26) and the cannula (27) into the ambient.
