diff --git a/extlib/benz/gc.c b/extlib/benz/gc.c
index fd0b048e..55e1c040 100644
--- a/extlib/benz/gc.c
+++ b/extlib/benz/gc.c
@@ -470,9 +470,6 @@ gc_mark_object(pic_state *pic, struct pic_object *obj)
     break;
   }
   case PIC_TT_SYMBOL: {
-    struct pic_symbol *sym = (struct pic_symbol *)obj;
-
-    gc_mark_object(pic, (struct pic_object *)sym->str);
     break;
   }
   case PIC_TT_REG: {
@@ -721,6 +718,8 @@ gc_finalize_object(pic_state *pic, struct pic_object *obj)
     break;
   }
   case PIC_TT_SYMBOL: {
+    pic_sym *sym = (pic_sym *)obj;
+    pic_free(pic, (void *)sym->cstr);
     break;
   }
   case PIC_TT_REG: {
@@ -751,16 +750,13 @@ gc_sweep_symbols(pic_state *pic)
   khash_t(s) *h = &pic->syms;
   khiter_t it;
   pic_sym *sym;
-  const char *cstr;
 
   for (it = kh_begin(h); it != kh_end(h); ++it) {
     if (! kh_exist(h, it))
       continue;
     sym = kh_val(h, it);
     if (! gc_obj_is_marked((struct pic_object *)sym)) {
-      cstr = kh_key(h, it);
       kh_del(s, h, it);
-      pic_free(pic, (void *)cstr);
     }
   }
 }
diff --git a/extlib/benz/include/picrin/symbol.h b/extlib/benz/include/picrin/symbol.h
index bb588d0d..601802c8 100644
--- a/extlib/benz/include/picrin/symbol.h
+++ b/extlib/benz/include/picrin/symbol.h
@@ -11,7 +11,7 @@ extern "C" {
 
 struct pic_symbol {
   PIC_OBJECT_HEADER
-  pic_str *str;
+  const char *cstr;
 };
 
 #define pic_sym_p(v) (pic_type(v) == PIC_TT_SYMBOL)
diff --git a/extlib/benz/state.c b/extlib/benz/state.c
index 7a419911..f334a23c 100644
--- a/extlib/benz/state.c
+++ b/extlib/benz/state.c
@@ -411,17 +411,8 @@ void
 pic_close(pic_state *pic)
 {
   khash_t(s) *h = &pic->syms;
-  khiter_t it;
   pic_allocf allocf = pic->allocf;
 
-  /* free all symbols */
-  for (it = kh_begin(h); it != kh_end(h); ++it) {
-    if (kh_exist(h, it)) {
-      allocf((void *)kh_key(h, it), 0);
-    }
-  }
-  kh_clear(s, h);
-
   /* clear out root objects */
   pic->sp = pic->stbase;
   pic->ci = pic->cibase;
diff --git a/extlib/benz/symbol.c b/extlib/benz/symbol.c
index 160d71ff..fcb5fb2d 100644
--- a/extlib/benz/symbol.c
+++ b/extlib/benz/symbol.c
@@ -6,52 +6,43 @@
 
 KHASH_DEFINE(s, const char *, pic_sym *, kh_str_hash_func, kh_str_hash_equal)
 
-static pic_sym *
-pic_make_symbol(pic_state *pic, pic_str *str)
-{
-  pic_sym *sym;
-
-  sym = (pic_sym *)pic_obj_alloc(pic, sizeof(struct pic_symbol), PIC_TT_SYMBOL);
-  sym->str = str;
-  return sym;
-}
-
 pic_sym *
 pic_intern(pic_state *pic, pic_str *str)
+{
+  return pic_intern_cstr(pic, pic_str_cstr(pic, str));
+}
+
+pic_sym *
+pic_intern_cstr(pic_state *pic, const char *cstr)
 {
   khash_t(s) *h = &pic->syms;
   pic_sym *sym;
-  char *cstr;
   khiter_t it;
   int ret;
+  char *copy;
 
-  it = kh_put(s, h, pic_str_cstr(pic, str), &ret);
+  it = kh_put(s, h, cstr, &ret);
   if (ret == 0) {               /* if exists */
     sym = kh_val(h, it);
     pic_gc_protect(pic, pic_obj_value(sym));
     return sym;
   }
 
-  cstr = pic_malloc(pic, pic_str_len(str) + 1);
-  strcpy(cstr, pic_str_cstr(pic, str));
-  kh_key(h, it) = cstr;
+  copy = pic_malloc(pic, strlen(cstr) + 1);
+  strcpy(copy, cstr);
+  kh_key(h, it) = copy;
 
-  sym = pic_make_symbol(pic, str);
+  sym = (pic_sym *)pic_obj_alloc(pic, sizeof(pic_sym), PIC_TT_SYMBOL);
+  sym->cstr = copy;
   kh_val(h, it) = sym;
 
   return sym;
 }
 
-pic_sym *
-pic_intern_cstr(pic_state *pic, const char *str)
-{
-  return pic_intern(pic, pic_make_str(pic, str, strlen(str)));
-}
-
 const char *
-pic_symbol_name(pic_state *pic, pic_sym *sym)
+pic_symbol_name(pic_state PIC_UNUSED(*pic), pic_sym *sym)
 {
-  return pic_str_cstr(pic, sym->str);
+  return sym->cstr;
 }
 
 static pic_value
@@ -90,7 +81,7 @@ pic_symbol_symbol_to_string(pic_state *pic)
 
   pic_get_args(pic, "m", &sym);
 
-  return pic_obj_value(sym->str);
+  return pic_obj_value(pic_make_str_cstr(pic, sym->cstr));
 }
 
 static pic_value