diff --git a/patoolib/util.py b/patoolib/util.py
index 6776747..292e8e6 100644
--- a/patoolib/util.py
+++ b/patoolib/util.py
@@ -260,14 +260,14 @@ def guess_mime_file_text (file_prog, filename):
     return None
 
 
-def check_existing_filename (filename):
+def check_existing_filename (filename, onlyfiles=True):
     """Ensure that given filename is a valid, existing file."""
-    if not os.path.isfile(filename):
-        raise PatoolError("`%s' is not a file" % filename)
     if not os.path.exists(filename):
         raise PatoolError("file `%s' was not found" % filename)
     if not os.access(filename, os.R_OK):
         raise PatoolError("file `%s' is not readable" % filename)
+    if onlyfiles and not os.path.isfile(filename):
+        raise PatoolError("`%s' is not a file" % filename)
 
 
 def check_new_filename (filename):
@@ -281,7 +281,7 @@ def check_archive_filelist (filenames):
     if not filenames:
         raise PatoolError("cannot create archive with empty filelist")
     for filename in filenames:
-        check_existing_filename(filename)
+        check_existing_filename(filename, onlyfiles=False)
 
 
 def set_mode (filename, flags):
@@ -405,6 +405,8 @@ def strlist_with_or (alist):
 
 def is_same_file (filename1, filename2):
     """Check if filename1 and filename2 point to the same file object."""
+    if filename1 == filename2:
+        return True
     if os.name == 'posix':
         return os.path.samefile(filename1, filename2)
     return os.path.realpath(filename1) == os.path.realpath(filename2)
diff --git a/tests/test_util.py b/tests/test_util.py
new file mode 100644
index 0000000..94c4a3b
--- /dev/null
+++ b/tests/test_util.py
@@ -0,0 +1,37 @@
+# -*- coding: utf-8 -*-
+# Copyright (C) 2010-2011 Bastian Kleineidam
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+import unittest
+import os
+import shutil
+from patoolib import util
+
+class UtilTest (unittest.TestCase):
+
+    def test_samefile1 (self):
+        filename1 = filename2 = __file__
+        self.assertTrue(util.is_same_file(filename1, filename2))
+
+    def test_samefile2 (self):
+        parentdir = os.path.dirname(__file__)
+        filename1 = os.path.dirname(parentdir)
+        filename2 = os.path.join(parentdir, '..')
+        self.assertTrue(util.is_same_file(filename1, filename2))
+
+    def test_samefile3 (self):
+        parentdir = os.path.dirname(__file__)
+        filename1 = os.path.dirname(parentdir)
+        filename2 = os.path.join(parentdir, '.')
+        self.assertFalse(util.is_same_file(filename1, filename2))