diff --git a/ChangeLog b/ChangeLog
index 53e748a083..25bea4852f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Aug 20 10:40:04 2010  Tanaka Akira  <akr@fsij.org>
+
+	* ext/pathname/pathname.c (path_expand_path): Pathname#expand_path
+	  translated from pathname.rb.
+
 Thu Aug 19 22:44:56 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* tool/make-snapshot (usage): add usage.
diff --git a/ext/pathname/lib/pathname.rb b/ext/pathname/lib/pathname.rb
index 54b06eefbc..2056477eef 100644
--- a/ext/pathname/lib/pathname.rb
+++ b/ext/pathname/lib/pathname.rb
@@ -512,9 +512,6 @@ end
 
 class Pathname    # * File *
 
-  # See <tt>File.expand_path</tt>.
-  def expand_path(*args) self.class.new(File.expand_path(@path, *args)) end
-
   # See <tt>File.split</tt>.  Returns the #dirname and the #basename in an
   # Array.
   def split() File.split(@path).map {|f| self.class.new(f) } end
diff --git a/ext/pathname/pathname.c b/ext/pathname/pathname.c
index 834fa446da..2ebb976de2 100644
--- a/ext/pathname/pathname.c
+++ b/ext/pathname/pathname.c
@@ -459,6 +459,21 @@ path_extname(VALUE self)
     return rb_funcall(rb_cFile, rb_intern("extname"), 1, str);
 }
 
+/*
+ * See <tt>File.expand_path</tt>.
+ */
+static VALUE
+path_expand_path(int argc, VALUE *argv, VALUE self)
+{
+    VALUE str = get_strpath(self);
+    VALUE dname;
+    if (rb_scan_args(argc, argv, "01", &dname) == 0)
+        str = rb_funcall(rb_cFile, rb_intern("expand_path"), 1, str);
+    else
+        str = rb_funcall(rb_cFile, rb_intern("expand_path"), 2, str, dname);
+    return rb_class_new_instance(1, &str, rb_obj_class(self));
+}
+
 /*
  * == Pathname
  *
@@ -681,4 +696,5 @@ Init_pathname()
     rb_define_method(rb_cPathname, "basename", path_basename, -1);
     rb_define_method(rb_cPathname, "dirname", path_dirname, 0);
     rb_define_method(rb_cPathname, "extname", path_extname, 0);
+    rb_define_method(rb_cPathname, "expand_path", path_expand_path, -1);
 }
diff --git a/test/pathname/test_pathname.rb b/test/pathname/test_pathname.rb
index 125eb39509..9adecb5b05 100644
--- a/test/pathname/test_pathname.rb
+++ b/test/pathname/test_pathname.rb
@@ -926,6 +926,14 @@ class TestPathname < Test::Unit::TestCase
     assert_equal(".ext", Pathname("basename.ext").extname)
   end
 
+  def test_expand_path
+    assert_equal(Pathname("/a"), Pathname("/a").expand_path)
+    assert_equal(Pathname("/a"), Pathname("a").expand_path("/"))
+    assert_equal(Pathname("/a"), Pathname("a").expand_path(Pathname("/")))
+    assert_equal(Pathname("/b"), Pathname("/b").expand_path(Pathname("/a")))
+    assert_equal(Pathname("/a/b"), Pathname("b").expand_path(Pathname("/a")))
+  end
+
   def test_split
     assert_equal([Pathname("dirname"), Pathname("basename")], Pathname("dirname/basename").split)
   end