The present invention relates to a disposable cartridge for a drug delivery device, the cartridge comprising: —a flexible bag (81; 181) to accommodate a liquid medicament and having an opening (81a, 181a) adjacent to a sidewall (81b, 181b), a socket (76, 176) having a fluid channel (86; 186) in fluid communication with a cartridge fluid coupling (90; 190), wherein the socket (76, 176) extends into the opening (81a, 181a) of the flexible bag (81; 181), a housing (71; 171) covering at least a portion of the flexible bag (81; 181) and having a receptacle (71a, 171a) to receive the socket (76; 176) with the flexible bag (81; 181), wherein the flexible bag's (81; 181) sidewall (81b; 181b) is fixed between the socket (76; 176) and the receptacle (71a, 171a).