Abstract: A draper header for harvesting crops includes a header frame with a middle frame section pivotally coupled between a pair of side wing sections. A cutter bar assembly extends across a front portion of the header frame and is flexible with the side wing sections for cutting the crops to be harvested. A pair of crop pick-up reels are rotatably supported by center and outer reel support arms for engaging the crops to be harvested. A sensing system is operatively coupled to the header frame for detecting when at least one of the side wing sections pivots downwardly relative to the middle frame section. When the sensing system detects that at least one of the side wing sections pivots downwardly past a predetermined pivot angle, a down-stop cylinder is actuated to raise the crop pick-up reels, thereby preventing contact of the crop pick-up reels with the cutter bar assembly.