diff --git a/contrib/10.callcc/callcc.c b/contrib/10.callcc/callcc.c
index 4388e8bb..68cbd4d9 100644
--- a/contrib/10.callcc/callcc.c
+++ b/contrib/10.callcc/callcc.c
@@ -276,8 +276,8 @@ pic_callcc_callcc(pic_state *pic)
   }
 }
 
-#define pic_redefun(pic, lib, name, func)       \
-  pic_set(pic, lib, name, pic_obj_value(pic_make_proc(pic, func, 0, NULL)))
+#define pic_redefun(pic, lib, name, func)                               \
+  pic_set(pic, lib, name, pic_obj_value(pic_lambda(pic, func, 0)))
 
 void
 pic_init_callcc(pic_state *pic)
diff --git a/contrib/40.srfi/src/106.c b/contrib/40.srfi/src/106.c
index ee26620e..e8029bc6 100644
--- a/contrib/40.srfi/src/106.c
+++ b/contrib/40.srfi/src/106.c
@@ -392,7 +392,7 @@ pic_init_srfi_106(pic_state *pic)
 {
   pic_deflibrary(pic, "srfi.106");
 
-#define pic_defun_(pic, name, f) pic_define(pic, "srfi.106", name, pic_obj_value(pic_make_proc(pic, f, 0, NULL)))
+#define pic_defun_(pic, name, f) pic_define(pic, "srfi.106", name, pic_obj_value(pic_lambda(pic, f, 0)))
 #define pic_define_(pic, name, v) pic_define(pic, "srfi.106", name, v)
 
   pic_defun_(pic, "socket?", pic_socket_socket_p);
diff --git a/extlib/benz/debug.c b/extlib/benz/debug.c
index 7bde1990..c9c8c2af 100644
--- a/extlib/benz/debug.c
+++ b/extlib/benz/debug.c
@@ -3,6 +3,7 @@
  */
 
 #include "picrin.h"
+#include "picrin/object.h"
 
 struct pic_string *
 pic_get_backtrace(pic_state *pic)
diff --git a/extlib/benz/error.c b/extlib/benz/error.c
index 39c2e9d9..658d85af 100644
--- a/extlib/benz/error.c
+++ b/extlib/benz/error.c
@@ -3,6 +3,7 @@
  */
 
 #include "picrin.h"
+#include "picrin/object.h"
 
 void
 pic_panic(pic_state PIC_UNUSED(*pic), const char *msg)
diff --git a/extlib/benz/include/picrin.h b/extlib/benz/include/picrin.h
index f0c85c9e..5f0c58f0 100644
--- a/extlib/benz/include/picrin.h
+++ b/extlib/benz/include/picrin.h
@@ -264,7 +264,6 @@ int pic_str_hash(pic_state *, struct pic_string *);
 #include "picrin/macro.h"
 #include "picrin/pair.h"
 #include "picrin/port.h"
-#include "picrin/proc.h"
 #include "picrin/record.h"
 #include "picrin/symbol.h"
 
diff --git a/extlib/benz/include/picrin/object.h b/extlib/benz/include/picrin/object.h
index 411d4d35..63473828 100644
--- a/extlib/benz/include/picrin/object.h
+++ b/extlib/benz/include/picrin/object.h
@@ -80,6 +80,48 @@ struct pic_data {
 #define pic_data_ptr(o) ((struct pic_data *)pic_obj_ptr(o))
 
 
+/* context */
+
+struct pic_context {
+  PIC_OBJECT_HEADER
+  pic_value *regs;
+  int regc;
+  struct pic_context *up;
+  pic_value storage[1];
+};
+
+#define pic_context_ptr(o) ((struct pic_context *)pic_obj_ptr(o))
+
+
+/* procedure */
+
+struct pic_proc {
+  PIC_OBJECT_HEADER
+  enum {
+    PIC_PROC_TAG_IREP,
+    PIC_PROC_TAG_FUNC
+  } tag;
+  union {
+    struct {
+      pic_func_t func;
+      int localc;
+    } f;
+    struct {
+      struct pic_irep *irep;
+      struct pic_context *cxt;
+    } i;
+  } u;
+  pic_value locals[1];
+};
+
+#define pic_proc_ptr(o) ((struct pic_proc *)pic_obj_ptr(o))
+
+#define pic_proc_func_p(proc) ((proc)->tag == PIC_PROC_TAG_FUNC)
+#define pic_proc_irep_p(proc) ((proc)->tag == PIC_PROC_TAG_IREP)
+
+struct pic_proc *pic_make_proc(pic_state *, pic_func_t, int, pic_value *);
+struct pic_proc *pic_make_proc_irep(pic_state *, struct pic_irep *, struct pic_context *);
+
 #if defined(__cplusplus)
 }
 #endif
diff --git a/extlib/benz/include/picrin/proc.h b/extlib/benz/include/picrin/proc.h
deleted file mode 100644
index 7fcbe509..00000000
--- a/extlib/benz/include/picrin/proc.h
+++ /dev/null
@@ -1,54 +0,0 @@
-/**
- * See Copyright Notice in picrin.h
- */
-
-#ifndef PICRIN_PROC_H
-#define PICRIN_PROC_H
-
-#if defined(__cplusplus)
-extern "C" {
-#endif
-
-struct pic_context {
-  PIC_OBJECT_HEADER
-  pic_value *regs;
-  int regc;
-  struct pic_context *up;
-  pic_value storage[1];
-};
-
-struct pic_proc {
-  PIC_OBJECT_HEADER
-  enum {
-    PIC_PROC_TAG_IREP,
-    PIC_PROC_TAG_FUNC
-  } tag;
-  union {
-    struct {
-      pic_func_t func;
-      int localc;
-    } f;
-    struct {
-      struct pic_irep *irep;
-      struct pic_context *cxt;
-    } i;
-  } u;
-  pic_value locals[1];
-};
-
-#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_proc_ptr(o) ((struct pic_proc *)pic_obj_ptr(o))
-
-#define pic_context_p(o) (pic_type(pic, o) == PIC_TYPE_CXT)
-#define pic_context_ptr(o) ((struct pic_context *)pic_obj_ptr(o))
-
-struct pic_proc *pic_make_proc(pic_state *, pic_func_t, int, pic_value *);
-struct pic_proc *pic_make_proc_irep(pic_state *, struct pic_irep *, struct pic_context *);
-
-#if defined(__cplusplus)
-}
-#endif
-
-#endif
diff --git a/extlib/benz/macro.c b/extlib/benz/macro.c
index 8a65f594..c6572765 100644
--- a/extlib/benz/macro.c
+++ b/extlib/benz/macro.c
@@ -3,6 +3,7 @@
  */
 
 #include "picrin.h"
+#include "picrin/object.h"
 
 KHASH_DEFINE(env, pic_id *, pic_sym *, kh_ptr_hash_func, kh_ptr_hash_equal)