diff --git a/extlib/benz/debug.c b/extlib/benz/debug.c
index 189f95dc..ae3ca9b3 100644
--- a/extlib/benz/debug.c
+++ b/extlib/benz/debug.c
@@ -22,7 +22,7 @@ pic_get_backtrace(pic_state *pic)
     trace = pic_str_cat(pic, trace, pic_lit_value(pic, "  at "));
     trace = pic_str_cat(pic, trace, pic_lit_value(pic, "(anonymous lambda)"));
 
-    if (pic_proc_func_p(pic_proc_ptr(pic, proc))) {
+    if (pic_func_p(proc)) {
       trace = pic_str_cat(pic, trace, pic_lit_value(pic, " (native function)\n"));
     } else {
       trace = pic_str_cat(pic, trace, pic_lit_value(pic, " (unknown location)\n")); /* TODO */
diff --git a/extlib/benz/gc.c b/extlib/benz/gc.c
index 00a34de5..f5ecd292 100644
--- a/extlib/benz/gc.c
+++ b/extlib/benz/gc.c
@@ -301,16 +301,16 @@ gc_mark_object(pic_state *pic, struct object *obj)
     }
     break;
   }
-  case PIC_TYPE_PROC: {
-    if (pic_proc_irep_p(&obj->u.proc)) {
-      if (obj->u.proc.u.i.cxt) {
-        LOOP(obj->u.proc.u.i.cxt);
-      }
-    } else {
-      int i;
-      for (i = 0; i < obj->u.proc.u.f.localc; ++i) {
-        gc_mark(pic, obj->u.proc.locals[i]);
-      }
+  case PIC_TYPE_FUNC: {
+    int i;
+    for (i = 0; i < obj->u.proc.u.f.localc; ++i) {
+      gc_mark(pic, obj->u.proc.locals[i]);
+    }
+    break;
+  }
+  case PIC_TYPE_IREP: {
+    if (obj->u.proc.u.i.cxt) {
+      LOOP(obj->u.proc.u.i.cxt);
     }
     break;
   }
@@ -550,10 +550,8 @@ gc_finalize_object(pic_state *pic, struct object *obj)
     kh_destroy(weak, &obj->u.weak.hash);
     break;
   }
-  case PIC_TYPE_PROC: {
-    if (pic_proc_irep_p(&obj->u.proc)) {
-      pic_irep_decref(pic, obj->u.proc.u.i.irep);
-    }
+  case PIC_TYPE_IREP: {
+    pic_irep_decref(pic, obj->u.proc.u.i.irep);
     break;
   }
 
@@ -564,6 +562,7 @@ gc_finalize_object(pic_state *pic, struct object *obj)
   case PIC_TYPE_ID:
   case PIC_TYPE_RECORD:
   case PIC_TYPE_CP:
+  case PIC_TYPE_FUNC:
     break;
 
   default:
diff --git a/extlib/benz/include/picrin.h b/extlib/benz/include/picrin.h
index 7147991f..c422833e 100644
--- a/extlib/benz/include/picrin.h
+++ b/extlib/benz/include/picrin.h
@@ -162,7 +162,6 @@ enum {
   PIC_TYPE_STRING  = 16,
   PIC_TYPE_VECTOR  = 17,
   PIC_TYPE_BLOB    = 18,
-  PIC_TYPE_PROC    = 19,
   PIC_TYPE_PORT    = 20,
   PIC_TYPE_ERROR   = 21,
   PIC_TYPE_ID      = 22,
@@ -174,7 +173,9 @@ enum {
   PIC_TYPE_SYMBOL  = 28,
   PIC_TYPE_PAIR    = 29,
   PIC_TYPE_CXT     = 30,
-  PIC_TYPE_CP      = 31
+  PIC_TYPE_CP      = 31,
+  PIC_TYPE_FUNC    = 32,
+  PIC_TYPE_IREP    = 33,
 };
 
 #define pic_invalid_p(pic,v) (pic_type(pic,v) == PIC_TYPE_INVALID)
@@ -185,9 +186,10 @@ enum {
 #define pic_eof_p(pic, v) (pic_type(pic, v) == PIC_TYPE_EOF)
 #define pic_true_p(pic,v) (pic_type(pic,v) == PIC_TYPE_TRUE)
 #define pic_false_p(pic,v) (pic_type(pic,v) == PIC_TYPE_FALSE)
+#define pic_id_p(pic, v) (pic_type(pic, v) == PIC_TYPE_ID || pic_type(pic, v) == PIC_TYPE_SYMBOL)
 #define pic_str_p(pic,v) (pic_type(pic,v) == PIC_TYPE_STRING)
 #define pic_blob_p(pic,v) (pic_type(pic,v) == PIC_TYPE_BLOB)
-#define pic_proc_p(pic,v) (pic_type(pic,v) == PIC_TYPE_PROC)
+#define pic_proc_p(pic,v) (pic_type(pic,v) == PIC_TYPE_FUNC || pic_type(pic, v) == PIC_TYPE_IREP)
 #define pic_nil_p(pic,v) (pic_type(pic,v) == PIC_TYPE_NIL)
 #define pic_pair_p(pic,v) (pic_type(pic,v) == PIC_TYPE_PAIR)
 #define pic_vec_p(pic,v) (pic_type(pic,v) == PIC_TYPE_VECTOR)
diff --git a/extlib/benz/include/picrin/private/object.h b/extlib/benz/include/picrin/private/object.h
index 39751196..64b1d6d9 100644
--- a/extlib/benz/include/picrin/private/object.h
+++ b/extlib/benz/include/picrin/private/object.h
@@ -93,10 +93,6 @@ struct context {
 
 struct proc {
   PIC_OBJECT_HEADER
-  enum {
-    PIC_PROC_TAG_IREP,
-    PIC_PROC_TAG_FUNC
-  } tag;
   union {
     struct {
       pic_func_t func;
@@ -158,7 +154,6 @@ struct object *pic_obj_ptr(pic_value);
 #define pic_env_p(pic, v) (pic_type(pic, v) == PIC_TYPE_ENV)
 #define pic_error_p(pic, v) (pic_type(pic, v) == PIC_TYPE_ERROR)
 #define pic_rec_p(pic, v) (pic_type(pic, v) == PIC_TYPE_RECORD)
-#define pic_id_p(pic, v) (pic_type(pic, v) == PIC_TYPE_ID || pic_type(pic, v) == PIC_TYPE_SYMBOL)
 
 pic_value pic_obj_value(void *ptr);
 struct object *pic_obj_alloc(pic_state *, size_t, int type);
@@ -191,8 +186,8 @@ pic_value pic_id_name(pic_state *, pic_value id);
 void pic_rope_incref(pic_state *, struct rope *);
 void pic_rope_decref(pic_state *, struct rope *);
 
-#define pic_proc_func_p(proc) ((proc)->tag == PIC_PROC_TAG_FUNC)
-#define pic_proc_irep_p(proc) ((proc)->tag == PIC_PROC_TAG_IREP)
+#define pic_func_p(proc) (pic_type(pic, proc) == PIC_TYPE_FUNC)
+#define pic_irep_p(proc) (pic_type(pic, proc) == PIC_TYPE_IREP)
 
 void pic_wind(pic_state *, struct checkpoint *, struct checkpoint *);
 
diff --git a/extlib/benz/proc.c b/extlib/benz/proc.c
index 301dd09d..9b9070d2 100644
--- a/extlib/benz/proc.c
+++ b/extlib/benz/proc.c
@@ -503,7 +503,7 @@ pic_apply(pic_state *pic, pic_value proc, int argc, pic_value *argv)
       ci->fp = pic->sp - c.a;
       ci->irep = NULL;
       ci->cxt = NULL;
-      if (pic_proc_func_p(proc)) {
+      if (proc->tt == PIC_TYPE_FUNC) {
 
         /* invoke! */
         v = proc->u.f.func(pic);
@@ -904,27 +904,27 @@ pic_set(pic_state *pic, const char *lib, const char *name, pic_value val)
 pic_value
 pic_closure_ref(pic_state *pic, int n)
 {
-  struct proc *self = pic_proc_ptr(pic, GET_OPERAND(pic, 0));
+  pic_value self = GET_OPERAND(pic, 0);
 
-  assert(pic_proc_func_p(self));
+  assert(pic_func_p(self));
 
-  if (n < 0 || self->u.f.localc <= n) {
+  if (n < 0 || pic_proc_ptr(pic, self)->u.f.localc <= n) {
     pic_errorf(pic, "pic_closure_ref: index out of range (%d)", n);
   }
-  return self->locals[n];
+  return pic_proc_ptr(pic, self)->locals[n];
 }
 
 void
 pic_closure_set(pic_state *pic, int n, pic_value v)
 {
-  struct proc *self = pic_proc_ptr(pic, GET_OPERAND(pic, 0));
+  pic_value self = GET_OPERAND(pic, 0);
 
-  assert(pic_proc_func_p(self));
+  assert(pic_func_p(self));
 
-  if (n < 0 || self->u.f.localc <= n) {
+  if (n < 0 || pic_proc_ptr(pic, self)->u.f.localc <= n) {
     pic_errorf(pic, "pic_closure_ref: index out of range (%d)", n);
   }
-  self->locals[n] = v;
+  pic_proc_ptr(pic, self)->locals[n] = v;
 }
 
 pic_value
@@ -979,8 +979,7 @@ pic_make_proc(pic_state *pic, pic_func_t func, int n, pic_value *env)
   struct proc *proc;
   int i;
 
-  proc = (struct proc *)pic_obj_alloc(pic, offsetof(struct proc, locals) + sizeof(pic_value) * n, PIC_TYPE_PROC);
-  proc->tag = PIC_PROC_TAG_FUNC;
+  proc = (struct proc *)pic_obj_alloc(pic, offsetof(struct proc, locals) + sizeof(pic_value) * n, PIC_TYPE_FUNC);
   proc->u.f.func = func;
   proc->u.f.localc = n;
   for (i = 0; i < n; ++i) {
@@ -994,8 +993,7 @@ pic_make_proc_irep(pic_state *pic, struct irep *irep, struct context *cxt)
 {
   struct proc *proc;
 
-  proc = (struct proc *)pic_obj_alloc(pic, offsetof(struct proc, locals), PIC_TYPE_PROC);
-  proc->tag = PIC_PROC_TAG_IREP;
+  proc = (struct proc *)pic_obj_alloc(pic, offsetof(struct proc, locals), PIC_TYPE_IREP);
   proc->u.i.irep = irep;
   proc->u.i.cxt = cxt;
   pic_irep_incref(pic, irep);
diff --git a/extlib/benz/value.c b/extlib/benz/value.c
index bd2d1e8e..a41d7d52 100644
--- a/extlib/benz/value.c
+++ b/extlib/benz/value.c
@@ -240,7 +240,8 @@ pic_typename(pic_state *pic, int type)
     return "identifier";
   case PIC_TYPE_CXT:
     return "context";
-  case PIC_TYPE_PROC:
+  case PIC_TYPE_FUNC:
+  case PIC_TYPE_IREP:
     return "procedure";
   case PIC_TYPE_ENV:
     return "environment";