Mapkit background pattern drawn on screen while using canDrawMapRect

While rendering tiles in a background thread by using canDrawMapRect (and returning NO), Mapkit draws a background pattern where the tiles eventually get drawn on the screen (using drawMapRect). I’m not doing this with intent, canDrawMapRect doesn’t even get a screen context, so I’m not sure why this is happening. For debugging I delay running setNeedsDisplayInMapRect:zoomScale, and get to see the entire map area get drawn with this background pattern before we start returning YES from canDrawMapRect and MapKit calls drawMapRect to draw actual tile images. At full speed the tiles flash dark gray before actual map tiles are drawn. Is there a way to not redraw the background pattern?