diff --git a/circList.ml b/circList.ml
index 9a63e380..fda92d1f 100644
--- a/circList.ml
+++ b/circList.ml
@@ -45,7 +45,9 @@ let make f f_len r r_len = match f with
 
 let singleton x = make [x] 1 [] 0
 
-let of_list l = make l (List.length l) [] 0
+let of_list l =
+  if l = [] then raise (Invalid_argument "empty list");
+  make l (List.length l) [] 0
 
 let length l = l.f_len + l.r_len
 
diff --git a/circList.mli b/circList.mli
index fdec46ef..9638e616 100644
--- a/circList.mli
+++ b/circList.mli
@@ -37,7 +37,8 @@ val singleton : 'a -> 'a t
 
 val of_list : 'a list -> 'a t
 (** build a circular list from a list. Linear in the length
-    of the list *)
+    of the list.
+    @raise Invalid_argument if the list is empty *)
 
 val length : 'a t -> int
 (** length of the cycle. *)
diff --git a/levenshtein.mli b/levenshtein.mli
index 0f4e5e87..d571415e 100644
--- a/levenshtein.mli
+++ b/levenshtein.mli
@@ -78,7 +78,7 @@ The signature for a given string representation provides 3 main things:
   maximal distance).
 
 A possible use of the index could be:
-[
+{[
 open Batteries;;
 
 let words = File.with_file_in "/usr/share/dict/english" 
@@ -88,6 +88,7 @@ let words = List.map (fun s->s,s) words;;
 let idx = Levenshtein.Index.of_list words;;
 
 Levenshtein.Index.retrieve ~limit:1 idx "hell" |> Levenshtein.klist_to_list;;
+]}
 *)
 
 module type S = sig