ocaml tail-recursive functions

I'm running Ocaml using utop, when I run the below function on a very long input:

let string_to_list str =  let rec loop i limit =    if i = limit then []    else (String.get str i) :: (loop (i + 1) limit)  in  loop 0 (String.length str);;

it returns the following error:

Stack overflow during evaluation (looping recursion?).

What would be the tail-recursive version of the function?