diff --git a/src/option.ml b/src/option.ml
index 5898eac7f64cfb9a9910ee3237719843666eea0a..ab66e8d471037e5b86e6243504436293dc951f58 100644
--- a/src/option.ml
+++ b/src/option.ml
@@ -18,3 +18,9 @@ let fold f o accu =
   | Some x ->
       f x accu
 
+let project = function
+  | Some x ->
+      x
+  | None ->
+      (* Presumably, an error message has already been printed. *)
+      exit 1
diff --git a/src/option.mli b/src/option.mli
index 832f63d717976e9539df3b3934e144d6119e9ab8..162e8325230182e8600d2b89ff1e2934e7d104d1 100644
--- a/src/option.mli
+++ b/src/option.mli
@@ -1,3 +1,4 @@
 val map: ('a -> 'b) -> 'a option -> 'b option
 val iter: ('a -> unit) -> 'a option -> unit
 val fold: ('a -> 'b -> 'b) -> 'a option -> 'b -> 'b
+val project: 'a option -> 'a (* careful: calls [exit 1] in case of failure *)