diff --git a/ChangeLog b/ChangeLog
index d16bb44391..f1fa5527e4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Jun 27 00:00:14 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* ruby.c (set_arg0, ruby_prog_init): freeze $0.  a patch from Keita
+	  Yamaguchi <keita.yamaguchi at gmail.com>.
+
 Thu Jun 26 23:58:29 2008  Yusuke Endoh  <mame@tsg.ne.jp>
 
 	* string.c (rb_str_index_m, rb_str_rindex_m, rb_str_include): fix
diff --git a/ruby.c b/ruby.c
index 027b15f051..26ed3f4917 100644
--- a/ruby.c
+++ b/ruby.c
@@ -1397,14 +1397,14 @@ set_arg0(VALUE val, ID id)
 	}
     }
 #endif
-    rb_progname = rb_tainted_str_new(s, i);
+    rb_progname = rb_obj_freeze(rb_tainted_str_new(s, i));
 }
 
 void
 ruby_script(const char *name)
 {
     if (name) {
-	rb_progname = rb_tainted_str_new2(name);
+	rb_progname = rb_obj_freeze(rb_tainted_str_new2(name));
     }
 }