diff --git a/extlib/benz/include/picrin.h b/extlib/benz/include/picrin.h
index ae728792..b8a2df83 100644
--- a/extlib/benz/include/picrin.h
+++ b/extlib/benz/include/picrin.h
@@ -175,8 +175,7 @@ bool pic_eq_p(pic_value, pic_value);
 bool pic_eqv_p(pic_value, pic_value);
 bool pic_equal_p(pic_state *, pic_value, pic_value);
 
-pic_sym pic_intern(pic_state *, const char *, size_t);
-pic_sym pic_intern_str(pic_state *, pic_str *);
+pic_sym pic_intern(pic_state *, pic_str *);
 pic_sym pic_intern_cstr(pic_state *, const char *);
 const char *pic_symbol_name(pic_state *, pic_sym);
 pic_sym pic_gensym(pic_state *, pic_sym);
diff --git a/extlib/benz/lib.c b/extlib/benz/lib.c
index 0e603fe4..f75ca99e 100644
--- a/extlib/benz/lib.c
+++ b/extlib/benz/lib.c
@@ -104,7 +104,7 @@ import_table(pic_state *pic, pic_value spec, struct pic_dict *imports)
 
       prefix = pic_list_ref(pic, spec, 2);
       pic_dict_for_each (sym, table) {
-        id = pic_intern_str(pic, pic_format(pic, "~s~s", prefix, pic_sym_value(sym)));
+        id = pic_intern(pic, pic_format(pic, "~s~s", prefix, pic_sym_value(sym)));
         pic_dict_set(pic, imports, id, pic_dict_ref(pic, table, sym));
       }
       return;
diff --git a/extlib/benz/read.c b/extlib/benz/read.c
index aed121a6..c416fa22 100644
--- a/extlib/benz/read.c
+++ b/extlib/benz/read.c
@@ -222,7 +222,8 @@ read_symbol(pic_state *pic, struct pic_port *port, const char *str)
     buf[len - 1] = (char)c;
   }
 
-  sym = pic_intern(pic, buf, len);
+  buf[len] = 0;
+  sym = pic_intern_cstr(pic, buf);
   pic_free(pic, buf);
 
   return pic_sym_value(sym);
diff --git a/extlib/benz/symbol.c b/extlib/benz/symbol.c
index c6d68c44..65c1e6d1 100644
--- a/extlib/benz/symbol.c
+++ b/extlib/benz/symbol.c
@@ -6,21 +6,20 @@
 #include "picrin/string.h"
 
 pic_sym
-pic_intern(pic_state *pic, const char *str, size_t len)
+pic_intern(pic_state *pic, pic_str *str)
 {
   char *cstr;
   xh_entry *e;
   pic_sym id;
 
-  cstr = (char *)pic_malloc(pic, len + 1);
-  cstr[len] = '\0';
-  memcpy(cstr, str, len);
-
-  e = xh_get_str(&pic->syms, cstr);
+  e = xh_get_str(&pic->syms, pic_str_cstr(str));
   if (e) {
     return xh_val(e, pic_sym);
   }
 
+  cstr = (char *)pic_malloc(pic, pic_strlen(str) + 1);
+  strcpy(cstr, pic_str_cstr(str));
+
   id = pic->sym_cnt++;
   xh_put_str(&pic->syms, cstr, &id);
   xh_put_int(&pic->sym_names, id, &cstr);
@@ -30,13 +29,7 @@ pic_intern(pic_state *pic, const char *str, size_t len)
 pic_sym
 pic_intern_cstr(pic_state *pic, const char *str)
 {
-  return pic_intern(pic, str, strlen(str));
-}
-
-pic_sym
-pic_intern_str(pic_state *pic, pic_str *str)
-{
-  return pic_intern_cstr(pic, pic_str_cstr(str));
+  return pic_intern(pic, pic_make_str(pic, str, strlen(str)));
 }
 
 pic_sym