diff --git a/sledge/nonstdlib/NS0.ml b/sledge/nonstdlib/NS0.ml
index c197ce0c3..9ca08dad7 100644
--- a/sledge/nonstdlib/NS0.ml
+++ b/sledge/nonstdlib/NS0.ml
@@ -76,15 +76,3 @@ let map_endo map t ~f =
         x' )
   in
   if !change then t' else t
-
-let filter_map_endo filter_map t ~f =
-  let change = ref false in
-  let t' =
-    filter_map t ~f:(fun x ->
-        let x'_opt = f x in
-        ( match x'_opt with
-        | Some x' when x' == x -> ()
-        | _ -> change := true ) ;
-        x'_opt )
-  in
-  if !change then t' else t
diff --git a/sledge/nonstdlib/list.ml b/sledge/nonstdlib/list.ml
index 014a1b594..f81eb47ce 100644
--- a/sledge/nonstdlib/list.ml
+++ b/sledge/nonstdlib/list.ml
@@ -47,7 +47,6 @@ let fold_option xs ~init ~f =
     (fold xs ~init ~f:(fun acc elt ->
          match f acc elt with Some res -> res | None -> return None ))
 
-let filter_map_endo t ~f = filter_map_endo filter_map t ~f
 let map_endo t ~f = map_endo map t ~f
 
 let rev_map_unzip xs ~f =
diff --git a/sledge/nonstdlib/list.mli b/sledge/nonstdlib/list.mli
index d5e8eb98d..8d9f77ef9 100644
--- a/sledge/nonstdlib/list.mli
+++ b/sledge/nonstdlib/list.mli
@@ -40,10 +40,6 @@ val map_endo : 'a t -> f:('a -> 'a) -> 'a t
 (** Like map, but specialized to require [f] to be an endofunction, which
     enables preserving [==] if [f] preserves [==] of every element. *)
 
-val filter_map_endo : 'a t -> f:('a -> 'a option) -> 'a t
-(** Like filter_map, but specialized to require [f] to be an endofunction,
-    which enables preserving [==] if [f] preserves [==] of every element. *)
-
 val rev_map_unzip : 'a t -> f:('a -> 'b * 'c) -> 'b list * 'c list
 (** [rev_map_unzip ~f xs] is [unzip (rev_map ~f xs)] but more efficient. *)