diff --git a/example/load.ml b/example/load.ml
index 15edacd..c15b466 100644
--- a/example/load.ml
+++ b/example/load.ml
@@ -1,9 +1,16 @@
 let ( / ) = Eio.Path.( / )
 
+let filter v =
+  let p =
+    Eio.Path.native_exn v |> String.split_on_char '/'
+    |> List.filter (fun s -> not (String.equal "" s))
+  in
+  not @@ List.exists (function "_build" | ".git" -> true | _ -> false) p
+
 let () =
   Eio_main.run @@ fun env ->
   Eio_mem.run @@ fun _ ->
-  let cwd = Eio.Stdenv.cwd env / "src" |> Eio_mem.Fs.load in
+  let cwd = Eio.Stdenv.cwd env |> Eio_mem.Fs.load ~filter in
   Eio.traceln "The following filesystem has been loaded into memory: %a..."
     Eio.Path.pp cwd;
   Eio_mem.Fs.tree ~depth:max_int Fmt.stdout cwd
diff --git a/src/eio_mem.ml b/src/eio_mem.ml
index 2fc4a03..fb029d2 100644
--- a/src/eio_mem.ml
+++ b/src/eio_mem.ml
@@ -121,7 +121,7 @@ module Fs = struct
     let dir = make_dir config in
     (dir, "/")
 
-  let load path =
+  let load ?(filter = fun _ -> true) path =
     Low_level.reset ();
     let start = Eio.Path.native_exn path in
     let stat = Eio.Path.stat ~follow:true path in
@@ -131,17 +131,24 @@ module Fs = struct
       let stat = Eio.Path.stat ~follow:false v in
       match stat.kind with
       | `Regular_file ->
-          Eio.Path.with_open_out ~create:(`If_missing stat.perm)
-            (switch_filesystem v)
-          @@ fun o ->
-          Eio.Path.with_open_in v @@ fun i -> Eio.Flow.copy i o
+          if not (filter v) then ()
+          else
+            Eio.Path.with_open_out ~create:(`If_missing stat.perm)
+              (switch_filesystem v)
+            @@ fun o ->
+            Eio.Path.with_open_in v @@ fun i -> Eio.Flow.copy i o
       | `Directory ->
-          Eio.Path.mkdirs ~exists_ok:true ~perm:stat.perm (switch_filesystem v);
+          if not (filter v) then ()
+          else
+            Eio.Path.mkdirs ~exists_ok:true ~perm:stat.perm
+              (switch_filesystem v);
           let fnames = Eio.Path.read_dir v in
           List.iter (fun fname -> make_fs Eio.Path.(v / fname)) fnames
       | `Symbolic_link ->
-          let link_to = Eio.Path.read_link v in
-          Eio.Path.symlink ~link_to (switch_filesystem v)
+          if not (filter v) then ()
+          else
+            let link_to = Eio.Path.read_link v in
+            Eio.Path.symlink ~link_to (switch_filesystem v)
       | _ -> Eio.traceln "Skipping %a" Eio.Path.pp v
     in
     make_fs path;
diff --git a/src/eio_mem.mli b/src/eio_mem.mli
index d4bd5c0..885e916 100644
--- a/src/eio_mem.mli
+++ b/src/eio_mem.mli
@@ -11,9 +11,15 @@ module Fs : sig
   val make : ?config:Config.t -> unit -> [ `Close | Eio.Fs.dir_ty ] Eio.Path.t
   (** Construct a fresh file-system using an optional configuration. *)
 
-  val load : Eio.Fs.dir_ty Eio.Path.t -> Eio.Fs.dir_ty Eio.Path.t
+  val load :
+    ?filter:(Eio.Fs.dir_ty Eio.Path.t -> bool) ->
+    Eio.Fs.dir_ty Eio.Path.t ->
+    Eio.Fs.dir_ty Eio.Path.t
   (** [load path] will reset the in-memory filesystem and fill it with the
-      directory tree at [path]. *)
+      directory tree at [path].
+
+      @param filter
+        Called on every path, if it returns [true] then this file is kept. *)
 
   val tree : depth:int -> _ Eio.Path.t Fmt.t
   (** A [tree]-like pretty printer. *)