A device for regulating the flow rate of air feeding a turbine ventilation cavity of a turbomachine turbine section is disclosed. The device includes at least one tubular duct opening into a take-off cavity and leading into a turbine ventilation cavity, the pressure inside the take-off cavity being higher than the pressure inside the turbine ventilation cavity; an air flow rate regulation valve disposed in the tubular duct, the valve being suitable for moving under the effect of the pressure difference between the take-off cavity and the turbine ventilation cavity; and a mechanical return device for holding the valve in a maximum closure position for the duct so long as the pressure difference between the take-off cavity and the turbine ventilation cavity remains below a predetermined threshold pressure.