diff --git a/day5.ml b/day5.ml
index 7f7c403..2873583 100644
--- a/day5.ml
+++ b/day5.ml
@@ -9,34 +9,34 @@ let rec find' ?(lo=0) ~hi = function
   | L::hs -> find' ~lo                 ~hi:(avg lo hi) hs
   | H::hs -> find' ~lo:(avg (lo+1) hi) ~hi             hs
 
-exception Inexact of bounds * int option [@warn_on_literal_pattern]
+exception Inexact of bounds [@warn_on_literal_pattern]
 
-let find ?index ?lo ~hi halves =
+let find ?lo ~hi halves =
   match find' ?lo ~hi halves with
   | Exact   x -> x
-  | Between p -> raise (Inexact (p, index))
+  | Between p -> raise (Inexact p)
 
 
 type path = {rows: half list; cols: half list}
 
-exception Unknown_char of char * int option
+exception Unknown_char of char [@warn_on_literal_pattern]
 
-let path_of_string ?index str =
+let path_of_string str =
   let revs {rows; cols} = List.{rows = rev rows; cols = rev cols} in
   let put acc = function
     | 'F' -> {acc with rows = L :: acc.rows}
     | 'B' -> {acc with rows = H :: acc.rows}
     | 'L' -> {acc with cols = L :: acc.cols}
     | 'R' -> {acc with cols = H :: acc.cols}
-    | c   -> raise (Unknown_char (c, index)) in
+    | c   -> raise (Unknown_char c) in
   String.to_seq str |> Seq.fold_left put {rows = []; cols = []} |> revs
 
 
 type seat = {row: int; col: int}
 
-let seat_of_path ?index {rows; cols} =
-  {row = find ?index ~hi:127 rows;
-   col = find ?index ~hi:7   cols}
+let seat_of_path {rows; cols} =
+  {row = find ~hi:127 rows;
+   col = find ~hi:7   cols}
 
 let seat_id {row; col} = (row * 8) + col