diff --git a/src/string_with_vars.ml b/src/string_with_vars.ml
index 05d9d2ff..66aca1c7 100644
--- a/src/string_with_vars.ml
+++ b/src/string_with_vars.ml
@@ -211,7 +211,7 @@ module Var = struct
 
   let to_string = string_of_var
 
-  let fail v ~f = Loc.fail (loc v) "%s" (f (to_string v))
+  let pp fmt t = Format.pp_print_string fmt (to_string t)
 
   let sexp_of_t t = Sexp.atom (to_string t)
 
diff --git a/src/string_with_vars.mli b/src/string_with_vars.mli
index 7dda300f..3bf6ee5b 100644
--- a/src/string_with_vars.mli
+++ b/src/string_with_vars.mli
@@ -49,6 +49,8 @@ end
 module Var : sig
   type t
 
+  val pp : t Fmt.t
+
   val sexp_of_t : t -> Sexp.t
 
   val loc : t -> Loc.t
@@ -60,8 +62,6 @@ module Var : sig
 
   val destruct : t -> kind
 
-  val fail : t -> f:(string -> string) -> _
-
   val to_string : t -> string
 
   val rename : t -> new_name:string -> t
diff --git a/src/super_context.ml b/src/super_context.ml
index e32cfa07..4649fbf6 100644
--- a/src/super_context.ml
+++ b/src/super_context.ml
@@ -242,19 +242,19 @@ end = struct
           if syntax_version >= min_version then
             Some v
           else
-            String_with_vars.Var.fail var ~f:(fun var ->
-              sprintf "Variable %s is available in since version %s. \
-                       Current version is %s"
-                var
-                (Syntax.Version.to_string min_version)
-                (Syntax.Version.to_string syntax_version))
+            Loc.fail (String_with_vars.Var.loc var)
+              "Variable %a is available in since version %s. \
+               Current version is %s"
+              String_with_vars.Var.pp var
+              (Syntax.Version.to_string min_version)
+              (Syntax.Version.to_string syntax_version)
         | Renamed_in (in_version, new_name) -> begin
             if syntax_version >= in_version then
-              String_with_vars.Var.fail var ~f:(fun old_name ->
-                sprintf "Variable %s has been renamed to %s since %s"
-                  old_name
-                  (String_with_vars.Var.(to_string (rename var ~new_name)))
-                  (Syntax.Version.to_string in_version))
+              Loc.fail (String_with_vars.Var.loc var)
+                "Variable %a has been renamed to %s since %s"
+                String_with_vars.Var.pp var
+                (String_with_vars.Var.(to_string (rename var ~new_name)))
+                (Syntax.Version.to_string in_version)
             else
               expand t ~syntax_version:in_version
                 ~var:(String_with_vars.Var.rename var ~new_name)
@@ -263,12 +263,12 @@ end = struct
           if syntax_version < in_version then
             Some v
           else
-            String_with_vars.Var.fail var ~f:(fun var ->
-              sprintf "Variable %s has been deleted in version %s. \
-                       Current version is: %s"
-                var
-                (Syntax.Version.to_string in_version)
-                (Syntax.Version.to_string syntax_version)))
+            Loc.fail (String_with_vars.Var.loc var)
+              "Variable %a has been deleted in version %s. \
+               Current version is: %s"
+              String_with_vars.Var.pp var
+              (Syntax.Version.to_string in_version)
+              (Syntax.Version.to_string syntax_version))
   end
 end
 
@@ -354,8 +354,9 @@ let (expand_vars_string, expand_vars_path) =
         begin match Var.Kind.to_value_no_deps_or_targets ~scope v with
         | Some _ as v -> v
         | None ->
-          String_with_vars.Var.fail var
-            ~f:(sprintf "Variable %s is not allowed in this context")
+          Loc.fail (String_with_vars.Var.loc var)
+            "Variable %a is not allowed in this context"
+            String_with_vars.Var.pp var
         end)
   in
   let expand_vars t ~scope ~dir ?extra_vars s =
@@ -938,7 +939,8 @@ module Action = struct
         end
       | Some Path_no_dep -> Some [Value.Dir (Path.relative dir s)]
       | None ->
-        String_with_vars.Var.fail var ~f:(sprintf "Unknown form: %s")
+        Loc.fail (String_with_vars.Var.loc var) "Unknown form: %a"
+          String_with_vars.Var.pp var
       end
     in
     let expand var syntax_version =