diff --git a/extlib/benz/data.c b/extlib/benz/data.c
index 00042286..c61989df 100644
--- a/extlib/benz/data.c
+++ b/extlib/benz/data.c
@@ -4,11 +4,12 @@ struct pic_data *
 pic_data_alloc(pic_state *pic, const pic_data_type *type, void *userdata)
 {
   struct pic_data *data;
+  struct pic_dict *storage = pic_make_dict(pic);
 
   data = (struct pic_data *)pic_obj_alloc(pic, sizeof(struct pic_data), PIC_TT_DATA);
   data->type = type;
   data->data = userdata;
-  xh_init_str(&data->storage, sizeof(pic_value));
+  data->storage = storage;
 
   return data;
 }
diff --git a/extlib/benz/dict.c b/extlib/benz/dict.c
index ca5d042d..41a4fea9 100644
--- a/extlib/benz/dict.c
+++ b/extlib/benz/dict.c
@@ -238,12 +238,13 @@ pic_dict_dictionary_to_alist(pic_state *pic)
 {
   struct pic_dict *dict;
   pic_value item, alist = pic_nil_value();
+  pic_sym *sym;
   xh_entry *it;
 
   pic_get_args(pic, "d", &dict);
 
-  for (it = xh_begin(&dict->hash); it != NULL; it = xh_next(it)) {
-    item = pic_cons(pic, pic_obj_value(xh_key(it, pic_sym *)), xh_val(it, pic_value));
+  pic_dict_for_each (sym, dict, it) {
+    item = pic_cons(pic, pic_obj_value(sym), pic_dict_ref(pic, dict, sym));
     pic_push(pic, item, alist);
   }
 
@@ -273,13 +274,14 @@ pic_dict_dictionary_to_plist(pic_state *pic)
 {
   struct pic_dict *dict;
   pic_value plist = pic_nil_value();
+  pic_sym *sym;
   xh_entry *it;
 
   pic_get_args(pic, "d", &dict);
 
-  for (it = xh_begin(&dict->hash); it != NULL; it = xh_next(it)) {
-    pic_push(pic, pic_obj_value(xh_key(it, pic_sym *)), plist);
-    pic_push(pic, xh_val(it, pic_value), plist);
+  pic_dict_for_each (sym, dict, it) {
+    pic_push(pic, pic_obj_value(sym), plist);
+    pic_push(pic, pic_dict_ref(pic, dict, sym), plist);
   }
 
   return pic_reverse(pic, plist);
diff --git a/extlib/benz/gc.c b/extlib/benz/gc.c
index 9205abe2..adf449ec 100644
--- a/extlib/benz/gc.c
+++ b/extlib/benz/gc.c
@@ -442,11 +442,8 @@ gc_mark_object(pic_state *pic, struct pic_object *obj)
   }
   case PIC_TT_DATA: {
     struct pic_data *data = (struct pic_data *)obj;
-    xh_entry *it;
 
-    for (it = xh_begin(&data->storage); it != NULL; it = xh_next(it)) {
-      gc_mark(pic, xh_val(it, pic_value));
-    }
+    gc_mark_object(pic, (struct pic_object *)data->storage);
     if (data->type->mark) {
       data->type->mark(pic, data->data, gc_mark);
     }
@@ -454,11 +451,12 @@ gc_mark_object(pic_state *pic, struct pic_object *obj)
   }
   case PIC_TT_DICT: {
     struct pic_dict *dict = (struct pic_dict *)obj;
+    pic_sym *sym;
     xh_entry *it;
 
-    for (it = xh_begin(&dict->hash); it != NULL; it = xh_next(it)) {
-      gc_mark_object(pic, (struct pic_object *)xh_key(it, pic_sym *));
-      gc_mark(pic, xh_val(it, pic_value));
+    pic_dict_for_each (sym, dict, it) {
+      gc_mark_object(pic, (struct pic_object *)sym);
+      gc_mark(pic, pic_dict_ref(pic, dict, sym));
     }
     break;
   }
@@ -705,7 +703,6 @@ gc_finalize_object(pic_state *pic, struct pic_object *obj)
     if (data->type->dtor) {
       data->type->dtor(pic, data->data);
     }
-    xh_destroy(&data->storage);
     break;
   }
   case PIC_TT_DICT: {
diff --git a/extlib/benz/include/picrin/data.h b/extlib/benz/include/picrin/data.h
index 38a20c3d..f527eee7 100644
--- a/extlib/benz/include/picrin/data.h
+++ b/extlib/benz/include/picrin/data.h
@@ -18,7 +18,7 @@ typedef struct {
 struct pic_data {
   PIC_OBJECT_HEADER
   const pic_data_type *type;
-  xhash storage;                /* const char * to pic_value table */
+  struct pic_dict *storage;
   void *data;
 };
 
diff --git a/extlib/benz/write.c b/extlib/benz/write.c
index e98e027c..c5ba08bb 100644
--- a/extlib/benz/write.c
+++ b/extlib/benz/write.c
@@ -169,6 +169,7 @@ write_core(struct writer_control *p, pic_value obj)
   pic_state *pic = p->pic;
   xFILE *file = p->file;
   size_t i;
+  pic_sym *sym;
   xh_entry *e, *it;
   int c;
 #if PIC_ENABLE_FLOAT
@@ -297,9 +298,9 @@ write_core(struct writer_control *p, pic_value obj)
     break;
   case PIC_TT_DICT:
     xfprintf(pic, file, "#.(dictionary");
-    for (it = xh_begin(&pic_dict_ptr(obj)->hash); it != NULL; it = xh_next(it)) {
-      xfprintf(pic, file, " '%s ", pic_symbol_name(pic, xh_key(it, pic_sym *)));
-      write_core(p, xh_val(it, pic_value));
+    pic_dict_for_each (sym, pic_dict_ptr(obj), it) {
+      xfprintf(pic, file, " '%s ", pic_symbol_name(pic, sym));
+      write_core(p, pic_dict_ref(pic, pic_dict_ptr(obj), sym));
     }
     xfprintf(pic, file, ")");
     break;