diff --git a/ChangeLog b/ChangeLog
index 72dde736cc..f0575c2c03 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu May  7 14:26:14 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* array.c (rb_ary_sample): negative sample number is invalid.
+	  [ruby-core:23374]
+
 Thu May  7 14:16:24 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* string.c, include/ruby/encoding.h: fixed types.
diff --git a/array.c b/array.c
index 198f0570f1..4eeae43391 100644
--- a/array.c
+++ b/array.c
@@ -3450,6 +3450,7 @@ rb_ary_sample(int argc, VALUE *argv, VALUE ary)
     }
     rb_scan_args(argc, argv, "1", &nv);
     n = NUM2LONG(nv);
+    if (n < 0) rb_raise(rb_eArgError, "negative sample number");
     ptr = RARRAY_PTR(ary);
     len = RARRAY_LEN(ary);
     if (n > len) n = len;
diff --git a/test/ruby/test_array.rb b/test/ruby/test_array.rb
index 9b3dfdf45f..a20c6b23cd 100644
--- a/test/ruby/test_array.rb
+++ b/test/ruby/test_array.rb
@@ -1605,6 +1605,8 @@ class TestArray < Test::Unit::TestCase
       end
       assert_operator(h.values.min * 2, :>=, h.values.max) if n != 0
     end
+
+    assert_raise(ArgumentError, '[ruby-core:23374]') {[1, 2].sample(-1)}
   end
 
   def test_cycle