Image Synopsis for Folder Lost After Closing and Reopening

I am able to set image synopses for folders by dragging images to the synopsis panel. These are then visible in the corkboard for the parent folder. However, after closing and reopening, all folder synopsis images are lost. The only thing that persists is the setting to display image synopsis instead of text, but all that means is once less step to drag-and-drop the image into the synopsis panel.