Abstract: Disclosed is a new air shutoff valve for a hopper gun for on/off control of inlet air synchronized to existing on/off control of texture coating mixture. The air shutoff valve comprises a tubular valve stem disposed within the air stem of the hopper gun. The valve stem has an air inlet port proximal a first end and an open second end. A valve control element controls airflow into the hopper gun by selectively obstructing the inlet aperture of the male quick disconnect air fitting. The valve control element comprises a resilient conical frustum-shaped plug disposed partially within the inlet end of the male fitting whereby pressurized air attempting to enter will seat the plug against the inlet aperture to stop airflow. The small end of the plug is fixedly connected to the first end of the valve stem.