[Elladan and Elrohir]

Another error, which Christopher Tolkien points out in The History of the Lord of the Rings, is the scene in Book II, Chapter III where Frodo and Gandalf notice a shadow in the sky. Gandalf says perhaps it was a small wisp of cloud, and Aragorn mutters "it was moving fast then, and not with the wind."

C.J.R.T. says this can be nothing other than a Nazgul, but points out that this cannot be, since, as is later made clear in Book III, the winged Nazgul had not yet crossed the River Anduin, being saved for other purposes. This was apparently a slip by Tolkien.