A grain tank 10 of an agricultural harvester is described having a top formed with an opening. A cover 12 overlies the opening, and a lifting mechanism 60,64,66,70 is provided for raising the cover 12 to an elevated position. Side panels 14,16,42 extend between the cover 12 and the top of the grain tank 10 when the cover 12 is in the elevated position to provide an enclosed extension volume that increases the storage capacity of the grain tank 10. At least two of the side panels 14 are rigidly and permanently connected to the cover 12.
