diff --git a/cont.c b/cont.c
index 695e39b0..c542399d 100644
--- a/cont.c
+++ b/cont.c
@@ -121,7 +121,7 @@ save_cont(pic_state *pic, struct pic_cont **c)
 
   cont = *c = (struct pic_cont *)pic_obj_alloc(pic, sizeof(struct pic_cont), PIC_TT_CONT);
 
-  cont->blk = pic->blk;
+  cont->wind = pic->wind;
 
   cont->stk_len = native_stack_length(pic, &pos);
   cont->stk_pos = pos;
@@ -168,7 +168,6 @@ restore_cont(pic_state *pic, struct pic_cont *cont)
 {
   char v;
   struct pic_cont *tmp = cont;
-  struct pic_block *blk;
 
   if (&v < pic->native_stack_start) {
     if (&v > cont->stk_pos) native_stack_extend(pic, cont);
@@ -177,8 +176,7 @@ restore_cont(pic_state *pic, struct pic_cont *cont)
     if (&v > cont->stk_pos + cont->stk_len) native_stack_extend(pic, cont);
   }
 
-  blk = pic->blk;
-  pic->blk = cont->blk;
+  pic->wind = cont->wind;
 
   pic->stbase = (pic_value *)pic_realloc(pic, pic->stbase, sizeof(pic_value) * cont->st_len);
   memcpy(pic->stbase, cont->st_ptr, sizeof(pic_value) * cont->st_len);
@@ -208,7 +206,7 @@ restore_cont(pic_state *pic, struct pic_cont *cont)
 }
 
 static void
-walk_to_block(pic_state *pic, struct pic_block *here, struct pic_block *there)
+walk_to_block(pic_state *pic, struct pic_winder *here, struct pic_winder *there)
 {
   if (here == there)
     return;
@@ -226,23 +224,23 @@ walk_to_block(pic_state *pic, struct pic_block *here, struct pic_block *there)
 static pic_value
 pic_dynamic_wind(pic_state *pic, struct pic_proc *in, struct pic_proc *thunk, struct pic_proc *out)
 {
-  struct pic_block *here;
+  struct pic_winder *here;
   pic_value val;
 
   if (in != NULL) {
     pic_apply0(pic, in);        /* enter */
   }
 
-  here = pic->blk;
-  pic->blk = (struct pic_block *)pic_obj_alloc(pic, sizeof(struct pic_block), PIC_TT_BLK);
-  pic->blk->prev = here;
-  pic->blk->depth = here->depth + 1;
-  pic->blk->in = in;
-  pic->blk->out = out;
+  here = pic->wind;
+  pic->wind = pic_alloc(pic, sizeof(struct pic_winder));
+  pic->wind->prev = here;
+  pic->wind->depth = here->depth + 1;
+  pic->wind->in = in;
+  pic->wind->out = out;
 
   val = pic_apply0(pic, thunk);
 
-  pic->blk = here;
+  pic->wind = here;
 
   if (out != NULL) {
     pic_apply0(pic, out);       /* exit */
@@ -266,7 +264,7 @@ cont_call(pic_state *pic)
   cont->results = pic_list_by_array(pic, argc, argv);
 
   /* execute guard handlers */
-  walk_to_block(pic, pic->blk, cont->blk);
+  walk_to_block(pic, pic->wind, cont->wind);
 
   restore_cont(pic, cont);
 }
diff --git a/gc.c b/gc.c
index 38be3150..15304788 100644
--- a/gc.c
+++ b/gc.c
@@ -333,6 +333,20 @@ gc_unmark(union header *p)
   p->s.mark = PIC_GC_UNMARK;
 }
 
+static void
+gc_mark_winder(pic_state *pic, struct pic_winder *wind)
+{
+  if (wind->prev) {
+    gc_mark_object(pic, (struct pic_object *)wind->prev);
+  }
+  if (wind->in) {
+    gc_mark_object(pic, (struct pic_object *)wind->in);
+  }
+  if (wind->out) {
+    gc_mark_object(pic, (struct pic_object *)wind->out);
+  }
+}
+
 static void
 gc_mark_object(pic_state *pic, struct pic_object *obj)
 {
@@ -404,8 +418,8 @@ gc_mark_object(pic_state *pic, struct pic_object *obj)
     pic_callinfo *ci;
     size_t i;
 
-    /* block */
-    gc_mark_object(pic, (struct pic_object *)cont->blk);
+    /* winder */
+    gc_mark_winder(pic, cont->wind);
 
     /* stack */
     for (stack = cont->st_ptr; stack != cont->st_ptr + cont->sp_offset; ++stack) {
@@ -504,20 +518,6 @@ gc_mark_object(pic_state *pic, struct pic_object *obj)
     }
     break;
   }
-  case PIC_TT_BLK: {
-    struct pic_block *blk = (struct pic_block *)obj;
-
-    if (blk->prev) {
-      gc_mark_object(pic, (struct pic_object *)blk->prev);
-    }
-    if (blk->in) {
-      gc_mark_object(pic, (struct pic_object *)blk->in);
-    }
-    if (blk->out) {
-      gc_mark_object(pic, (struct pic_object *)blk->out);
-    }
-    break;
-  }
   case PIC_TT_NIL:
   case PIC_TT_BOOL:
   case PIC_TT_FLOAT:
@@ -565,9 +565,9 @@ gc_mark_phase(pic_state *pic)
   size_t i, j;
   xh_entry *it;
 
-  /* block */
-  if (pic->blk) {
-    gc_mark_object(pic, (struct pic_object *)pic->blk);
+  /* winder */
+  if (pic->wind) {
+    gc_mark_winder(pic, pic->wind);
   }
 
   /* stack */
@@ -709,9 +709,6 @@ gc_finalize_object(pic_state *pic, struct pic_object *obj)
     xh_destroy(&rec->hash);
     break;
   }
-  case PIC_TT_BLK: {
-    break;
-  }
   case PIC_TT_NIL:
   case PIC_TT_BOOL:
   case PIC_TT_FLOAT:
diff --git a/include/picrin.h b/include/picrin.h
index 3df0c538..5bec9eb0 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -46,6 +46,13 @@ extern "C" {
 
 typedef struct pic_code pic_code;
 
+struct pic_winder {
+  struct pic_proc *in;
+  struct pic_proc *out;
+  int depth;
+  struct pic_winder *prev;
+};
+
 typedef struct {
   int argc, retc;
   pic_code *ip;
@@ -60,7 +67,7 @@ typedef struct {
   int argc;
   char **argv, **envp;
 
-  struct pic_block *blk;
+  struct pic_winder *wind;
 
   pic_value *sp;
   pic_value *stbase, *stend;
diff --git a/include/picrin/cont.h b/include/picrin/cont.h
index eeabb798..587a46d1 100644
--- a/include/picrin/cont.h
+++ b/include/picrin/cont.h
@@ -9,18 +9,11 @@
 extern "C" {
 #endif
 
-struct pic_block {
-  PIC_OBJECT_HEADER
-  struct pic_block *prev;
-  int depth;
-  struct pic_proc *in, *out;
-};
-
 struct pic_cont {
   PIC_OBJECT_HEADER
   jmp_buf jmp;
 
-  struct pic_block *blk;
+  struct pic_winder *wind;
 
   char *stk_pos, *stk_ptr;
   ptrdiff_t stk_len;
diff --git a/include/picrin/value.h b/include/picrin/value.h
index 6a211dc1..453e645a 100644
--- a/include/picrin/value.h
+++ b/include/picrin/value.h
@@ -125,7 +125,6 @@ enum pic_tt {
   PIC_TT_DATA,
   PIC_TT_DICT,
   PIC_TT_RECORD,
-  PIC_TT_BLK,
 };
 
 #define PIC_OBJECT_HEADER			\
@@ -274,8 +273,6 @@ pic_type_repr(enum pic_tt tt)
     return "dict";
   case PIC_TT_RECORD:
     return "record";
-  case PIC_TT_BLK:
-    return "block";
   }
   UNREACHABLE();
 }
diff --git a/state.c b/state.c
index b88f40a1..df9ba02c 100644
--- a/state.c
+++ b/state.c
@@ -27,7 +27,7 @@ pic_open(int argc, char *argv[], char **envp)
   pic = malloc(sizeof(pic_state));
 
   /* root block */
-  pic->blk = NULL;
+  pic->wind = NULL;
 
   /* command line */
   pic->argc = argc;
@@ -153,10 +153,10 @@ pic_open(int argc, char *argv[], char **envp)
   pic_gc_arena_restore(pic, ai);
 
   /* root block */
-  pic->blk = (struct pic_block *)pic_obj_alloc(pic, sizeof(struct pic_block), PIC_TT_BLK);
-  pic->blk->prev = NULL;
-  pic->blk->depth = 0;
-  pic->blk->in = pic->blk->out = NULL;
+  pic->wind = pic_alloc(pic, sizeof(struct pic_winder));
+  pic->wind->prev = NULL;
+  pic->wind->depth = 0;
+  pic->wind->in = pic->wind->out = NULL;
 
   /* init readers */
   pic_init_reader(pic);
@@ -182,11 +182,11 @@ pic_close(pic_state *pic)
   xh_entry *it;
 
   /* invoke exit handlers */
-  while (pic->blk) {
-    if (pic->blk->out) {
-      pic_apply0(pic, pic->blk->out);
+  while (pic->wind) {
+    if (pic->wind->out) {
+      pic_apply0(pic, pic->wind->out);
     }
-    pic->blk = pic->blk->prev;
+    pic->wind = pic->wind->prev;
   }
 
   /* clear out root objects */