diff --git a/vendors/Red-Black_Trees/PolyMap.ml b/vendors/Red-Black_Trees/PolyMap.ml
index 78ab1738c..0ed6e9d6d 100644
--- a/vendors/Red-Black_Trees/PolyMap.ml
+++ b/vendors/Red-Black_Trees/PolyMap.ml
@@ -23,19 +23,17 @@ let remove key map =
   let cmp k1 (k2,_) = map.cmp k1 k2 in
   {map with tree = RB.remove ~cmp key map.tree}
 
-exception Not_found
-
 let find key map =
   let cmp k1 (k2,_) = map.cmp k1 k2 in
   try snd (RB.find ~cmp key map.tree) with
-    RB.Not_found -> raise Not_found
+    Not_found -> raise Not_found
 
 let find_opt key map =
   try Some (find key map) with Not_found -> None
 
 let update key updater map =
   match updater (find_opt key map) with
-  | None -> failwith "TODO: RedBlackTrees: remove not implemented" (* TODO: remove key *)
+  | None -> remove key map
   | Some v -> add key v map
 
 let bindings map =
diff --git a/vendors/Red-Black_Trees/PolyMap.mli b/vendors/Red-Black_Trees/PolyMap.mli
index 01e0d1468..bff0e87ce 100644
--- a/vendors/Red-Black_Trees/PolyMap.mli
+++ b/vendors/Red-Black_Trees/PolyMap.mli
@@ -42,8 +42,6 @@ val remove : 'key -> ('key, 'value) t -> ('key, 'value) t
    [key] in the map [map]. If [key] is not bound in [map], the
    exception [Not_found] is raised. *)
 
-exception Not_found
-
 val find : 'key -> ('key, 'value) t -> 'value
 
 (* The value of the call [find_opt key map] is [Some value] if the key
diff --git a/vendors/Red-Black_Trees/PolySet.ml b/vendors/Red-Black_Trees/PolySet.ml
index 7bbc3d628..ab26380f2 100644
--- a/vendors/Red-Black_Trees/PolySet.ml
+++ b/vendors/Red-Black_Trees/PolySet.ml
@@ -17,11 +17,9 @@ let is_empty set = RB.is_empty set.tree
 
 let add elt set = {set with tree = RB.add ~cmp:set.cmp RB.New elt set.tree}
 
-exception Not_found
-
 let find elt set =
   try RB.find ~cmp:set.cmp elt set.tree with
-    RB.Not_found -> raise Not_found
+    Not_found -> raise Not_found
 
 let find_opt elt set = RB.find_opt ~cmp:set.cmp elt set.tree
 
diff --git a/vendors/Red-Black_Trees/PolySet.mli b/vendors/Red-Black_Trees/PolySet.mli
index b76ebfd97..c8eb4b6d4 100644
--- a/vendors/Red-Black_Trees/PolySet.mli
+++ b/vendors/Red-Black_Trees/PolySet.mli
@@ -38,8 +38,6 @@ val add : 'elt -> 'elt t -> 'elt t
    function of [set] (see [create]). If [elt] is not in [set], then
    the exception [Not_found] is raised. *)
 
-exception Not_found
-
 val find : 'elt -> 'elt t -> 'elt
 
 (* The call [find_opt elt set] is similar to [find elt set], except
diff --git a/vendors/Red-Black_Trees/RedBlack.ml b/vendors/Red-Black_Trees/RedBlack.ml
index 4241363dc..f77954d09 100644
--- a/vendors/Red-Black_Trees/RedBlack.ml
+++ b/vendors/Red-Black_Trees/RedBlack.ml
@@ -67,16 +67,15 @@ let remove : type a b . cmp:(a -> b -> int) -> a -> b t -> b t = fun ~cmp elt tr
             Int (colour, new_left, lroot, right)
        ) in
   let rec bst_delete : a -> b t -> b t = fun elt -> function
-    | Ext -> failwith "remove in red-black tree: element not found"
+    | Ext -> raise Not_found
     | Int (colour, left, root, right) as current ->
        let c = cmp elt root in
        if      c = 0 then bst_shift_up current
        else if c < 0 then Int (colour, bst_delete elt left, root, right)
        else               Int (colour, left, root, bst_delete elt right)
   in
-  bst_delete elt tree
-
-exception Not_found
+  try bst_delete elt tree
+  with Not_found -> tree
 
 let rec find ~cmp elt = function
   Ext -> raise Not_found
diff --git a/vendors/Red-Black_Trees/RedBlack.mli b/vendors/Red-Black_Trees/RedBlack.mli
index 9642da8e6..16d1f1a2e 100644
--- a/vendors/Red-Black_Trees/RedBlack.mli
+++ b/vendors/Red-Black_Trees/RedBlack.mli
@@ -39,8 +39,6 @@ val remove: cmp:('a -> 'b -> int) -> 'a -> 'b t -> 'b t
    to a node of the tree [t], such that [cmp x y = true]. If none, the
    exception [Not_found] is raised. *)
 
-exception Not_found
-
 val find: cmp:('a -> 'b -> int) -> 'a -> 'b t -> 'b
 
 (* The value of call [find_opt ~cmp x t] is [Some y] if there is an