diff --git a/ChangeLog b/ChangeLog
index ee9a9ae692..89224f04d3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Dec  2 17:00:54 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* encoding.c (enc_name, rb_enc_name_list_i, rb_enc_aliases_enc_i):
+	  make fstring instead of making each copies.
+
 Wed Dec  2 16:32:08 2015  Koichi Sasada  <ko1@atdot.net>
 
 	* iseq.h: introduce ISEQ_COMPILE_DATA() macro.
diff --git a/encoding.c b/encoding.c
index fe720767c2..eb777c90f3 100644
--- a/encoding.c
+++ b/encoding.c
@@ -1134,7 +1134,7 @@ enc_inspect(VALUE self)
 static VALUE
 enc_name(VALUE self)
 {
-    return rb_usascii_str_new2(rb_enc_name((rb_encoding*)DATA_PTR(self)));
+    return rb_fstring_cstr(rb_enc_name((rb_encoding*)DATA_PTR(self)));
 }
 
 static int
@@ -1633,8 +1633,7 @@ static int
 rb_enc_name_list_i(st_data_t name, st_data_t idx, st_data_t arg)
 {
     VALUE ary = (VALUE)arg;
-    VALUE str = rb_usascii_str_new2((char *)name);
-    OBJ_FREEZE(str);
+    VALUE str = rb_fstring_cstr((char *)name);
     rb_ary_push(ary, str);
     return ST_CONTINUE;
 }
@@ -1676,8 +1675,7 @@ rb_enc_aliases_enc_i(st_data_t name, st_data_t orig, st_data_t arg)
 	if (STRCASECMP((char*)name, rb_enc_name(enc)) == 0) {
 	    return ST_CONTINUE;
 	}
-	str = rb_usascii_str_new2(rb_enc_name(enc));
-	OBJ_FREEZE(str);
+	str = rb_fstring_cstr(rb_enc_name(enc));
 	rb_ary_store(ary, idx, str);
     }
     key = rb_usascii_str_new2((char *)name);