diff --git a/src/headers_lib.ml b/src/headers_lib.ml
index 357b9d0b..2357f897 100644
--- a/src/headers_lib.ml
+++ b/src/headers_lib.ml
@@ -57,6 +57,7 @@ end = struct
       Ok (String.sub s 1 (len - 2))
     else invalid_etag
 
+  (* TODO angstrom parser instead *)
   let parse s =
     if String.trim s = "*" then Ok Any_etag
     else