diff --git a/ChangeLog b/ChangeLog
index c2d9f135e5..c741c0f5b3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Feb 24 23:58:52 2009  Akinori MUSHA  <knu@iDaemons.org>
+
+	* array.c (rb_ary_index, rb_ary_rindex): Emit a warning that a
+	  given block is unused when an argument is specified.
+
 Tue Feb 24 22:00:37 2009  Tanaka Akira  <akr@fsij.org>
 
 	* ext/socket/socket.c (sockaddr_obj): convert fe80:1::1 to fe80::1%1.
diff --git a/array.c b/array.c
index 696b6473b5..79478649c2 100644
--- a/array.c
+++ b/array.c
@@ -1128,6 +1128,8 @@ rb_ary_index(int argc, VALUE *argv, VALUE ary)
 	return Qnil;
     }
     rb_scan_args(argc, argv, "1", &val);
+    if (rb_block_given_p())
+	rb_warn("given block not used");
     for (i=0; i<RARRAY_LEN(ary); i++) {
 	if (rb_equal(RARRAY_PTR(ary)[i], val))
 	    return LONG2NUM(i);
@@ -1168,6 +1170,8 @@ rb_ary_rindex(int argc, VALUE *argv, VALUE ary)
 	return Qnil;
     }
     rb_scan_args(argc, argv, "1", &val);
+    if (rb_block_given_p())
+	rb_warn("given block not used");
     while (i--) {
 	if (rb_equal(RARRAY_PTR(ary)[i], val))
 	    return LONG2NUM(i);