diff --git a/ChangeLog b/ChangeLog
index dda6f0c99f..c877140053 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Fri Jul 17 16:45:22 2009  Tanaka Akira  <akr@fsij.org>
+
+	* array.c (recursive_hash): reject recursive key.
+
 Fri Jul 17 15:20:53 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* random.c (DIGSPERINT): fix for LP64.
diff --git a/array.c b/array.c
index d8f787c029..a0dc6434ea 100644
--- a/array.c
+++ b/array.c
@@ -2884,7 +2884,7 @@ recursive_hash(VALUE ary, VALUE dummy, int recur)
     VALUE n;
 
     if (recur) {
-	return LONG2FIX(0);
+        rb_raise(rb_eArgError, "recursive key for hash");
     }
     h = rb_hash_start(RARRAY_LEN(ary));
     for (i=0; i<RARRAY_LEN(ary); i++) {
diff --git a/test/ruby/test_array.rb b/test/ruby/test_array.rb
index 489b401574..2723b37c6a 100644
--- a/test/ruby/test_array.rb
+++ b/test/ruby/test_array.rb
@@ -1572,9 +1572,7 @@ class TestArray < Test::Unit::TestCase
   def test_hash2
     a = []
     a << a
-    b = []
-    b << b
-    assert_equal(a.hash, b.hash)
+    assert_raise(ArgumentError) { a.hash }
   end
 
   def test_flatten2