diff --git a/eval.c b/eval.c
index 6c9ada77..d7e0bc93 100644
--- a/eval.c
+++ b/eval.c
@@ -400,15 +400,15 @@ static sexp sexp_make_macro (sexp ctx, sexp p, sexp e) {
 }
 
 sexp sexp_make_variable_transformer_op (sexp ctx, sexp self, sexp_sint_t n, sexp base_proc) {
+  sexp flags;
   sexp_assert_type(ctx, sexp_procedurep, SEXP_PROCEDURE, base_proc);
   if (sexp_procedure_variable_transformer_p(base_proc))
     return base_proc;
-  sexp vt_proc = sexp_alloc_type(ctx, procedure, SEXP_PROCEDURE);
-  sexp_procedure_flags(vt_proc) = (char) (sexp_uint_t) sexp_make_fixnum (sexp_unbox_fixnum(sexp_procedure_flags(base_proc)) | SEXP_PROC_VARIABLE_TRANSFORMER);
-  sexp_procedure_num_args(vt_proc) = sexp_procedure_num_args(base_proc);
-  sexp_procedure_code(vt_proc) =  sexp_procedure_code(base_proc);
-  sexp_procedure_vars(vt_proc) = sexp_procedure_vars(base_proc);
-  return vt_proc;
+  flags = sexp_make_fixnum(sexp_unbox_fixnum(sexp_procedure_flags(base_proc)) | SEXP_PROC_VARIABLE_TRANSFORMER);
+  return sexp_make_procedure(ctx, flags,
+                             sexp_make_fixnum(sexp_procedure_num_args(base_proc)),
+                             sexp_procedure_code(base_proc),
+                             sexp_procedure_vars(base_proc));
 }
 
 sexp sexp_make_synclo_op (sexp ctx, sexp self, sexp_sint_t n, sexp env, sexp fv, sexp expr) {