The invention relates to a side airbag module for an automotive vehicle which includes an inflatable bag (11) configured to be deployed between an occupant and the vehicle body upon being filled with the gas produced by a generator, which bag comprises a front panel (21) intended to make contact with the occupant, a rear panel (23) and at least one inner panel (25) forming a first chamber (13) with the rear panel (23) and a second chamber (15) with the front panel (21), having a vent hole (19), the inner panel (25) including a duct (39) allowing the passage of gas from the first chamber (13) to the second chamber (15) and which is located in a position allowing it to be blocked upon the front panel (21) moving closer to the inner panel (25) during the contact of the bag (11) with the occupant.