diff --git a/include/picrin/cont.h b/include/picrin/cont.h
index 67c86f6c..38cfc131 100644
--- a/include/picrin/cont.h
+++ b/include/picrin/cont.h
@@ -40,7 +40,7 @@ struct pic_cont {
   } while (0)
 
 #define PIC_BLK_DECREF(pic,blk) do {			\
-    pic_block *_a = (blk), *_b;			\
+    pic_block *_a = (blk), *_b;                         \
     while (_a) {					\
       if (! --_a->refcnt) {				\
 	_b = _a->prev;					\
@@ -52,6 +52,17 @@ struct pic_cont {
     }							\
   } while (0)
 
+#define PIC_BLK_EXIT(pic) do {                           \
+    pic_block *_a;                                       \
+    while (pic->blk) {                                   \
+      if (pic->blk->out)                                 \
+        pic_apply_argv(pic, pic->blk->out, 0);           \
+      _a = pic->blk->prev;                               \
+      PIC_BLK_DECREF(pic, pic->blk);                     \
+      pic->blk = _a;                                     \
+    }                                                    \
+  } while (0)
+
 pic_value pic_values(pic_state *, size_t, ...);
 pic_value pic_values_by_array(pic_state *, size_t, pic_value *);
 pic_value pic_values_by_list(pic_state *, pic_value);
diff --git a/src/system.c b/src/system.c
index 2591fa20..b5108af1 100644
--- a/src/system.c
+++ b/src/system.c
@@ -7,6 +7,7 @@
 #include "picrin.h"
 #include "picrin/string.h"
 #include "picrin/pair.h"
+#include "picrin/cont.h"
 
 static pic_value
 pic_system_cmdline(pic_state *pic)
@@ -31,7 +32,6 @@ pic_system_exit(pic_state *pic)
 {
   pic_value v;
   int argc, status = EXIT_SUCCESS;
-  pic_block *blk;
 
   argc = pic_get_args(pic, "|o", &v);
   if (argc == 1) {
@@ -47,11 +47,7 @@ pic_system_exit(pic_state *pic)
     }
   }
 
-  blk = pic->blk;
-  while (blk) {
-    pic_apply_argv(pic, blk->out, 0);
-    blk = blk->prev;
-  }
+  PIC_BLK_EXIT(pic);
 
   exit(status);
 }