diff --git a/ChangeLog b/ChangeLog
index ab57cfac7d..a7544fa261 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Wed Mar 14 08:06:35 2012  Shugo Maeda  <shugo@ruby-lang.org>
+
+	* enumerator.c (lazy_zip): add Enumerable::Lazy#flat_map.
+
+	* enumerator.c (lazy_lazy): just returns self.
+
 Wed Mar 14 07:48:36 2012  Tadayoshi Funaba  <tadf@dotrb.org>
 
 	* ext/date/date_core.c (datetime_s_now): [ruby-core:43256].
diff --git a/enumerator.c b/enumerator.c
index 5e91673899..65e750e7ba 100644
--- a/enumerator.c
+++ b/enumerator.c
@@ -1388,6 +1388,63 @@ lazy_grep(VALUE obj, VALUE pattern)
     return rb_block_call(rb_cLazy, id_new, 1, &obj, lazy_grep_func, pattern);
 }
 
+static VALUE
+lazy_zip_func_i(VALUE val, VALUE arg, int argc, VALUE *argv)
+{
+    VALUE yielder, ary, v, result;
+    int i;
+
+    yielder = argv[0];
+    ary = rb_ary_new2(RARRAY_LEN(arg) + 1);
+    rb_ary_push(ary, argv[1]);
+    for (i = 0; i < RARRAY_LEN(arg); i++) {
+	v = rb_funcall(RARRAY_PTR(arg)[i], rb_intern("next"), 0);
+	rb_ary_push(ary, v);
+    }
+    result = rb_yield(ary);
+    rb_funcall(yielder, id_yield, 1, result);
+    return Qnil;
+}
+
+static VALUE
+lazy_zip_func(VALUE val, VALUE arg, int argc, VALUE *argv)
+{
+    VALUE yielder, ary, v;
+    int i;
+
+    yielder = argv[0];
+    ary = rb_ary_new2(RARRAY_LEN(arg) + 1);
+    rb_ary_push(ary, argv[1]);
+    for (i = 0; i < RARRAY_LEN(arg); i++) {
+	v = rb_funcall(RARRAY_PTR(arg)[i], rb_intern("next"), 0);
+	rb_ary_push(ary, v);
+    }
+    rb_funcall(yielder, id_yield, 1, ary);
+    return Qnil;
+}
+
+static VALUE
+lazy_zip(int argc, VALUE *argv, VALUE obj)
+{
+    VALUE ary;
+    int i;
+
+    ary = rb_ary_new2(argc);
+    for (i = 0; i < argc; i++) {
+	rb_ary_push(ary, rb_funcall(argv[i], rb_intern("lazy"), 0));
+    }
+
+    return rb_block_call(rb_cLazy, id_new, 1, &obj,
+			 rb_block_given_p() ? lazy_zip_func_i :  lazy_zip_func,
+			 ary);
+}
+
+static VALUE
+lazy_lazy(VALUE obj)
+{
+    return obj;
+}
+
 static VALUE
 stop_result(VALUE self)
 {
@@ -1428,6 +1485,8 @@ Init_Enumerator(void)
     rb_define_method(rb_cLazy, "select", lazy_select, 0);
     rb_define_method(rb_cLazy, "reject", lazy_reject, 0);
     rb_define_method(rb_cLazy, "grep", lazy_grep, 1);
+    rb_define_method(rb_cLazy, "zip", lazy_zip, -1);
+    rb_define_method(rb_cLazy, "lazy", lazy_lazy, 0);
 
     rb_define_alias(rb_cLazy, "collect", "map");
     rb_define_alias(rb_cLazy, "collect_concat", "flat_map");
diff --git a/test/ruby/test_lazy_enumerator.rb b/test/ruby/test_lazy_enumerator.rb
index 9b74429a7f..6d96438454 100644
--- a/test/ruby/test_lazy_enumerator.rb
+++ b/test/ruby/test_lazy_enumerator.rb
@@ -109,4 +109,26 @@ class TestLazyEnumerator < Test::Unit::TestCase
     assert_equal('c', a.lazy.grep(/c/).first)
     assert_equal('c', a.current)
   end
+
+  def test_zip
+    a = Step.new(1..3)
+    assert_equal([1, "a"], a.zip("a".."c").first)
+    assert_equal(3, a.current)
+    assert_equal([1, "a"], a.lazy.zip("a".."c").first)
+    assert_equal(1, a.current)
+  end
+ 
+  def test_zip_without_arg
+    a = Step.new(1..3)
+    assert_equal([1], a.zip.first)
+    assert_equal(3, a.current)
+    assert_equal([1], a.lazy.zip.first)
+    assert_equal(1, a.current)
+  end
+
+  def test_zip_with_block
+    a = Step.new(1..3)
+    assert_equal(["a", 1], a.lazy.zip("a".."c") {|x, y| [y, x]}.first)
+    assert_equal(1, a.current)
+  end
 end