only can bind a horse to a fence, when having another lead in my hand

I can't bind a horse to a fence, if i don't have another lead in my hand. I expected that it would work if i bound a horse to me (with a lead) but i need to have another lead in my hand, so if i have another lead in my hand, i can bind the horse to the fence and once i have done that i still have this lead in my inventory!