diff --git a/extlib/benz/cont.c b/extlib/benz/cont.c
index 79fc747d..df1beedb 100644
--- a/extlib/benz/cont.c
+++ b/extlib/benz/cont.c
@@ -31,7 +31,7 @@ pic_dynamic_wind(pic_state *pic, struct pic_proc *in, struct pic_proc *thunk, st
   }
 
   here = pic->cp;
-  pic->cp = pic_malloc(pic, sizeof(pic_checkpoint));
+  pic->cp = (pic_checkpoint *)pic_obj_alloc(pic, sizeof(pic_checkpoint), PIC_TT_CP);
   pic->cp->prev = here;
   pic->cp->depth = here->depth + 1;
   pic->cp->in = in;
diff --git a/extlib/benz/gc.c b/extlib/benz/gc.c
index 59ea6850..d5cf55f0 100644
--- a/extlib/benz/gc.c
+++ b/extlib/benz/gc.c
@@ -329,20 +329,6 @@ gc_unmark(union header *p)
   p->s.mark = PIC_GC_UNMARK;
 }
 
-static void
-gc_mark_checkpoint(pic_state *pic, pic_checkpoint *cp)
-{
-  if (cp->prev) {
-    gc_mark_object(pic, (struct pic_object *)cp->prev);
-  }
-  if (cp->in) {
-    gc_mark_object(pic, (struct pic_object *)cp->in);
-  }
-  if (cp->out) {
-    gc_mark_object(pic, (struct pic_object *)cp->out);
-  }
-}
-
 static void
 gc_mark_object(pic_state *pic, struct pic_object *obj)
 {
@@ -495,6 +481,20 @@ gc_mark_object(pic_state *pic, struct pic_object *obj)
     pic->regs = reg;
     break;
   }
+  case PIC_TT_CP: {
+    struct pic_checkpoint *cp = (struct pic_checkpoint *)obj;
+
+    if (cp->prev) {
+      gc_mark_object(pic, (struct pic_object *)cp->prev);
+    }
+    if (cp->in) {
+      gc_mark_object(pic, (struct pic_object *)cp->in);
+    }
+    if (cp->out) {
+      gc_mark_object(pic, (struct pic_object *)cp->out);
+    }
+    break;
+  }
   case PIC_TT_NIL:
   case PIC_TT_BOOL:
 #if PIC_ENABLE_FLOAT
@@ -565,7 +565,7 @@ gc_mark_phase(pic_state *pic)
 
   /* checkpoint */
   if (pic->cp) {
-    gc_mark_checkpoint(pic, pic->cp);
+    gc_mark_object(pic, (struct pic_object *)pic->cp);
   }
 
   /* stack */
@@ -722,6 +722,9 @@ gc_finalize_object(pic_state *pic, struct pic_object *obj)
     xh_destroy(&reg->hash);
     break;
   }
+  case PIC_TT_CP: {
+    break;
+  }
   case PIC_TT_NIL:
   case PIC_TT_BOOL:
 #if PIC_ENABLE_FLOAT
diff --git a/extlib/benz/include/picrin.h b/extlib/benz/include/picrin.h
index 373a3fa6..01220cfd 100644
--- a/extlib/benz/include/picrin.h
+++ b/extlib/benz/include/picrin.h
@@ -53,6 +53,7 @@ typedef struct pic_jmpbuf {
 } pic_jmpbuf;
 
 typedef struct pic_checkpoint {
+  PIC_OBJECT_HEADER
   struct pic_proc *in;
   struct pic_proc *out;
   int depth;
diff --git a/extlib/benz/include/picrin/value.h b/extlib/benz/include/picrin/value.h
index 703bcb8e..507832bb 100644
--- a/extlib/benz/include/picrin/value.h
+++ b/extlib/benz/include/picrin/value.h
@@ -158,14 +158,15 @@ enum pic_tt {
   PIC_TT_PORT,
   PIC_TT_ERROR,
   PIC_TT_ID,
-  PIC_TT_CXT,
   PIC_TT_ENV,
   PIC_TT_LIB,
-  PIC_TT_IREP,
   PIC_TT_DATA,
   PIC_TT_DICT,
   PIC_TT_REG,
-  PIC_TT_RECORD
+  PIC_TT_RECORD,
+  PIC_TT_CXT,
+  PIC_TT_IREP,
+  PIC_TT_CP
 };
 
 #define PIC_OBJECT_HEADER			\
@@ -336,6 +337,8 @@ pic_type_repr(enum pic_tt tt)
     return "reg";
   case PIC_TT_RECORD:
     return "record";
+  case PIC_TT_CP:
+    return "checkpoint";
   }
   PIC_UNREACHABLE();
 }
diff --git a/extlib/benz/state.c b/extlib/benz/state.c
index fec9536f..46e88ab7 100644
--- a/extlib/benz/state.c
+++ b/extlib/benz/state.c
@@ -355,7 +355,7 @@ pic_open(int argc, char *argv[], char **envp, pic_allocf allocf)
   pic->attrs = pic_make_reg(pic);
 
   /* root block */
-  pic->cp = pic_malloc(pic, sizeof(pic_checkpoint));
+  pic->cp = (pic_checkpoint *)pic_obj_alloc(pic, sizeof(pic_checkpoint), PIC_TT_CP);
   pic->cp->prev = NULL;
   pic->cp->depth = 0;
   pic->cp->in = pic->cp->out = NULL;
@@ -401,14 +401,6 @@ pic_close(pic_state *pic)
   xh_entry *it;
   pic_allocf allocf = pic->allocf;
 
-  /* invoke exit handlers */
-  while (pic->cp) {
-    if (pic->cp->out) {
-      pic_apply0(pic, pic->cp->out);
-    }
-    pic->cp = pic->cp->prev;
-  }
-
   /* free symbol names */
   for (it = xh_begin(&pic->syms); it != NULL; it = xh_next(it)) {
     allocf(xh_key(it, char *), 0);