diff --git a/src/libraries/utils/filepath.ml b/src/libraries/utils/filepath.ml
index 2d78d5983034c8de67c10c1a1a9d5d5c5f5ee19f..a9719dc39c36377dff12a0bf43e6c0d4a6cbd232 100644
--- a/src/libraries/utils/filepath.ml
+++ b/src/libraries/utils/filepath.ml
@@ -224,6 +224,7 @@ module Normalized = struct
   let pretty fmt p = Format.fprintf fmt "%s" (pretty p)
   let pp_abs fmt p = Format.fprintf fmt "%s" p
   let unknown = normalize ""
+  let is_unknown fp = equal fp unknown
 end
 
 type position =
diff --git a/src/libraries/utils/filepath.mli b/src/libraries/utils/filepath.mli
index 5825faaf39666c6e7fa0cfb130c33dae5333797b..2afff02a14dece4316164ba48727895002f224bf 100644
--- a/src/libraries/utils/filepath.mli
+++ b/src/libraries/utils/filepath.mli
@@ -120,6 +120,9 @@ module Normalized: sig
 
   (** Unknown filepath, used as 'dummy' for [Datatype.Filepath]. *)
   val unknown: t
+
+  (** @since Frama-C+dev *)
+  val is_unknown: t -> bool
 end
 
 (** Describes a position in a source file.