diff --git a/sledge/src/fol/trm.ml b/sledge/src/fol/trm.ml
index 944fd0b31..8e654e84f 100644
--- a/sledge/src/fol/trm.ml
+++ b/sledge/src/fol/trm.ml
@@ -167,7 +167,7 @@ module Var = struct
 
     let freshen v ~wrt = fresh (name v) ~wrt
 
-    let identified ?(name = "") ~id =
+    let identified ~name ~id =
       assert (id > 0) ;
       make ~id:(id - Int.max_int) ~name
 
diff --git a/sledge/src/fol/var_intf.ml b/sledge/src/fol/var_intf.ml
index 17e7ba1fe..9f2144faa 100644
--- a/sledge/src/fol/var_intf.ml
+++ b/sledge/src/fol/var_intf.ml
@@ -33,9 +33,9 @@ module type S = sig
   val name : t -> string
   val fresh : string -> wrt:Set.t -> t * Set.t
 
-  val identified : ?name:string -> id:int -> t
-  (** Create a variable identified by [id] with optional [name]. The [id]
-      uniquely identifies the variable, and must be positive. *)
+  val identified : name:string -> id:int -> t
+  (** Create a variable identified by [id]. The [id] uniquely identifies the
+      variable, and must be positive. *)
 
   (** Variable renaming substitutions *)
   module Subst : Subst.S with type var := t with type set := Set.t