Struts coming loose?

It was the front nut. There is no roll pin hole, and there is no locking washer. Just the frame, thick rubber washer, thick metal concave washer and then this nut. I suppose I could put a large split locking washer under the nut? At least for piece of mind?

The ones with no cotter pin use a self locking nut. (crimped castle nut)
Blue Locktite will solve that for you.