A backrest fixation system (1) for a wheelchair, wherein the backrest fixation system (1) comprises a seat frame member (3) having a groove side (3a) provided with a first groove (5) having first groove retaining surfaces, which seat frame member (3) has a first lateral side (3b) and a second lateral side (3c) parallel to each other and which define lateral sides of the groove side (3a), a first groove insert member (9) arranged in the first groove (5) and retained in the first groove (5) by means of the first groove retaining surfaces, a backrest attachment member (15) having a first backrest attachment member through-opening (15a), a first fastener (17), and a reinforcement member (13) arranged between the backrest attachment member (15) and the groove side (3a) of the seat frame member (3), which reinforcement member (13) has a first leg (13a) and a second leg (13b), wherein the first leg (13a) extends along the first lateral side (3b) of the seat frame member (3) and the second leg (13b) extends along the second lateral side (3c) of the seat frame member (3), wherein the first groove insert member (9) is provided with a first groove insert member through-opening (9a) and the reinforcement member (13) is provided with a first reinforcement member through-opening (13d), and wherein the first fastener (17) extends through the first backrest attachment member through-opening (15a), the first reinforcement member through-opening (13d), and the first groove insert member through-opening (9a). An electrically powered wheelchair comprising a backrest fixation system is also presented herein.
