diff --git a/core/CCOpt.ml b/core/CCOpt.ml
index 40bd8e58..b99176de 100644
--- a/core/CCOpt.ml
+++ b/core/CCOpt.ml
@@ -84,6 +84,10 @@ let map2 f o1 o2 = match o1, o2 with
   | _, None -> None
   | Some x, Some y -> Some (f x y)
 
+let filter p = function
+  | Some x as o when p x -> o
+  | o -> o
+
 let iter f o = match o with
   | None -> ()
   | Some x -> f x
diff --git a/core/CCOpt.mli b/core/CCOpt.mli
index 48b7ec4a..838f04e7 100644
--- a/core/CCOpt.mli
+++ b/core/CCOpt.mli
@@ -60,6 +60,11 @@ val iter : ('a -> unit) -> 'a t -> unit
 val fold : ('a -> 'b -> 'a) -> 'a -> 'b t -> 'a
 (** Fold on 0 or 1 elements *)
 
+val filter : ('a -> bool) -> 'a t -> 'a t
+(** Filter on 0 or 1 elements
+
+    @since NEXT_RELEASE *)
+
 val get : 'a -> 'a t -> 'a
 (** [get default x] unwraps [x], but if [x = None] it returns [default] instead.
     @since NEXT_RELEASE *)