diff --git a/src/extPervasives.ml b/src/extPervasives.ml
index 0ea8bd5d..23ed113b 100644
--- a/src/extPervasives.ml
+++ b/src/extPervasives.ml
@@ -255,17 +255,3 @@ let lines s =
 
 let string_last_line s =
   lines s |> list_last
-
-let escape ?(chars="\\\"") ?(esc='\\') s =
-  let buf = Bytes.create (2 * String.length s) in
-  let j = ref 0 in
-  for i = 0 to String.length s - 1 do
-    if String.contains chars s.[i] then
-      (
-        Bytes.set buf !j esc;
-        incr j
-      );
-    Bytes.set buf !j s.[i];
-    incr j
-  done;
-  Bytes.sub_string buf 0 !j
diff --git a/src/jsonHelpers.ml b/src/jsonHelpers.ml
index 64cfb9d1..5b3c7c46 100644
--- a/src/jsonHelpers.ml
+++ b/src/jsonHelpers.ml
@@ -65,7 +65,7 @@ let json_to_dot cout json =
          nodeid
       | `String name ->
          let nodeid = fresh () in
-         fprintf cout "%s [label=\"%s\"];\n" nodeid (ExtPervasives.escape name);
+         fprintf cout "%s [label=\"%s\"];\n" nodeid (String.escaped name);
          nodeid
       | `List [x] ->
          traverse x
@@ -76,7 +76,7 @@ let json_to_dot cout json =
          List.iter (fun c -> fprintf cout "%s -> %s;\n" nodeid c) childrenids;
          nodeid
       | _ ->
-         failwith "unsupported feature in json_to_dot"
+         assert false
     in
     fprintf cout "digraph {\n";
     ignore (traverse json);