2 files changed, 11 insertions, 1 deletions
diff --git a/ChangeLog b/ChangeLog
index f55f52b4b6..aee1dd95c2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Jan 22 12:19:29 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* gc.c (define_final): cannot define finalizer for immediate
+	  values.  [ruby-core:21500]
+
 Thu Jan 22 11:33:08 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* thread.c (rb_time_timeval): made a real prototype.  a patch from
diff --git a/gc.c b/gc.c
index d56d2d170a..2d4da31a75 100644
--- a/gc.c
+++ b/gc.c
@@ -2290,9 +2290,14 @@ define_final(int argc, VALUE *argv, VALUE os)
 	rb_raise(rb_eArgError, "wrong type argument %s (should be callable)",
 		 rb_obj_classname(block));
     }
-    FL_SET(obj, FL_FINALIZE);
+    if (!FL_ABLE(obj)) {
+	rb_raise(rb_eArgError, "cannot define finalizer for %s",
+		 rb_obj_classname(obj));
+    }
+    RBASIC(obj)->flags |= FL_FINALIZE;
 
     block = rb_ary_new3(2, INT2FIX(rb_safe_level()), block);
+    OBJ_FREEZE(block);
 
     if (!finalizer_table) {
 	finalizer_table = st_init_numtable();