AIR DUCT O'HEAT on takeoff roll

[mlb406]

Every time I take off with the AIR SOURCE SELECT on BOTH as the checklist recommends, I get an AIR DUCT O'HEAT master caution. This warning doesn't pop up if the AIR SOURCE SELECT switch is positioned to OFF and then BOTH after departure. Is this a mistake in the checklist or aircraft? It happens when I set the N1 value given on the TO perf popout panel.