diff --git a/extlib/benz/bool.c b/extlib/benz/bool.c
index ff7d4a31..19c856cb 100644
--- a/extlib/benz/bool.c
+++ b/extlib/benz/bool.c
@@ -3,6 +3,7 @@
  */
 
 #include "picrin.h"
+#include "picrin/object.h"
 
 #if PIC_NAN_BOXING
 
diff --git a/extlib/benz/cont.c b/extlib/benz/cont.c
index 80ce6c54..4a43c9cf 100644
--- a/extlib/benz/cont.c
+++ b/extlib/benz/cont.c
@@ -3,6 +3,7 @@
  */
 
 #include "picrin.h"
+#include "picrin/object.h"
 
 void
 pic_wind(pic_state *pic, pic_checkpoint *here, pic_checkpoint *there)
diff --git a/extlib/benz/eval.c b/extlib/benz/eval.c
index 371651c6..43992d2e 100644
--- a/extlib/benz/eval.c
+++ b/extlib/benz/eval.c
@@ -3,6 +3,7 @@
  */
 
 #include "picrin.h"
+#include "picrin/object.h"
 #include "picrin/opcode.h"
 
 static pic_value
diff --git a/extlib/benz/include/picrin.h b/extlib/benz/include/picrin.h
index 47d5b16e..606af64f 100644
--- a/extlib/benz/include/picrin.h
+++ b/extlib/benz/include/picrin.h
@@ -270,7 +270,6 @@ int pic_str_hash(pic_state *, struct pic_string *);
 #include "picrin/record.h"
 #include "picrin/string.h"
 #include "picrin/symbol.h"
-#include "picrin/vector.h"
 
 void *pic_default_allocf(void *, void *, size_t);
 
diff --git a/extlib/benz/include/picrin/object.h b/extlib/benz/include/picrin/object.h
index bef9590f..b362f95c 100644
--- a/extlib/benz/include/picrin/object.h
+++ b/extlib/benz/include/picrin/object.h
@@ -9,6 +9,20 @@
 extern "C" {
 #endif
 
+
+/* vector */
+
+struct pic_vector {
+  PIC_OBJECT_HEADER
+  pic_value *data;
+  int len;
+};
+
+#define pic_vec_ptr(o) ((struct pic_vector *)pic_obj_ptr(o))
+
+
+/* weak */
+
 KHASH_DECLARE(weak, void *, pic_value)
 
 struct pic_weak {
diff --git a/extlib/benz/include/picrin/vector.h b/extlib/benz/include/picrin/vector.h
deleted file mode 100644
index bb5ddad1..00000000
--- a/extlib/benz/include/picrin/vector.h
+++ /dev/null
@@ -1,24 +0,0 @@
-/**
- * See Copyright Notice in picrin.h
- */
-
-#ifndef PICRIN_VECTOR_H
-#define PICRIN_VECTOR_H
-
-#if defined(__cplusplus)
-extern "C" {
-#endif
-
-struct pic_vector {
-  PIC_OBJECT_HEADER
-  pic_value *data;
-  int len;
-};
-
-#define pic_vec_ptr(o) ((struct pic_vector *)pic_obj_ptr(o))
-
-#if defined(__cplusplus)
-}
-#endif
-
-#endif
diff --git a/extlib/benz/proc.c b/extlib/benz/proc.c
index c77c9a9a..b8b54339 100644
--- a/extlib/benz/proc.c
+++ b/extlib/benz/proc.c
@@ -3,6 +3,7 @@
  */
 
 #include "picrin.h"
+#include "picrin/object.h"
 #include "picrin/opcode.h"
 
 #define MIN(x,y) ((x) < (y) ? (x) : (y))
diff --git a/extlib/benz/read.c b/extlib/benz/read.c
index 172e02db..84738f2c 100644
--- a/extlib/benz/read.c
+++ b/extlib/benz/read.c
@@ -3,6 +3,7 @@
  */
 
 #include "picrin.h"
+#include "picrin/object.h"
 
 KHASH_DEFINE(read, int, pic_value, kh_int_hash_func, kh_int_hash_equal)
 
diff --git a/extlib/benz/vector.c b/extlib/benz/vector.c
index 358ad54e..965d46e3 100644
--- a/extlib/benz/vector.c
+++ b/extlib/benz/vector.c
@@ -3,6 +3,7 @@
  */
 
 #include "picrin.h"
+#include "picrin/object.h"
 
 struct pic_vector *
 pic_make_vec(pic_state *pic, int len)
diff --git a/extlib/benz/write.c b/extlib/benz/write.c
index 73bba09e..9e3e2a50 100644
--- a/extlib/benz/write.c
+++ b/extlib/benz/write.c
@@ -3,6 +3,7 @@
  */
 
 #include "picrin.h"
+#include "picrin/object.h"
 
 KHASH_DECLARE(l, void *, int)
 KHASH_DECLARE(v, void *, int)