diff --git a/Lib/distutils/command/sdist.py b/Lib/distutils/command/sdist.py
--- a/Lib/distutils/command/sdist.py
+++ b/Lib/distutils/command/sdist.py
@@ -350,7 +350,8 @@ class sdist(Command):
     def write_manifest(self):
         """Write the file list in 'self.filelist' (presumably as filled in
         by 'add_defaults()' and 'read_template()') to the manifest file
-        named by 'self.manifest'.
+        named by 'self.manifest'.  All paths will use '/' as separator, for
+        cross-platform portability.
         """
         if os.path.isfile(self.manifest):
             fp = open(self.manifest)
@@ -366,6 +367,11 @@ class sdist(Command):
 
         content = self.filelist.files[:]
         content.insert(0, '# file GENERATED by distutils, do NOT edit')
+
+        # always use / as path separator in MANIFEST
+        #if os.sep != '/':
+        #    content = [line.replace(os.sep, '/') for line in content]
+
         self.execute(file_util.write_file, (self.manifest, content),
                      "writing manifest file '%s'" % self.manifest)
 
diff --git a/Lib/distutils/tests/test_sdist.py b/Lib/distutils/tests/test_sdist.py
--- a/Lib/distutils/tests/test_sdist.py
+++ b/Lib/distutils/tests/test_sdist.py
@@ -1,9 +1,9 @@
 """Tests for distutils.command.sdist."""
 import os
 import unittest
-import shutil
 import zipfile
 import tarfile
+import warnings
 
 # zlib is not used here, but if it's not available
 # the tests that use zipfile may fail
@@ -20,18 +20,15 @@ except ImportError:
     UID_GID_SUPPORT = False
 
 from os.path import join
-import sys
-import tempfile
-import warnings
+from textwrap import dedent
 
 from test.test_support import captured_stdout, check_warnings, run_unittest
 
 from distutils.command.sdist import sdist, show_formats
 from distutils.core import Distribution
 from distutils.tests.test_config import PyPIRCCommandTestCase
-from distutils.errors import DistutilsExecError, DistutilsOptionError
+from distutils.errors import DistutilsOptionError
 from distutils.spawn import find_executable
-from distutils.tests import support
 from distutils.log import WARN
 from distutils.archive_util import ARCHIVE_FORMATS
 
@@ -47,13 +44,13 @@ MANIFEST = """\
 README
 inroot.txt
 setup.py
-data%(sep)sdata.dt
-scripts%(sep)sscript.py
-some%(sep)sfile.txt
-some%(sep)sother_file.txt
-somecode%(sep)s__init__.py
-somecode%(sep)sdoc.dat
-somecode%(sep)sdoc.txt
+data/data.dt
+scripts/script.py
+some/file.txt
+some/other_file.txt
+somecode/__init__.py
+somecode/doc.dat
+somecode/doc.txt
 """
 
 class SDistTestCase(PyPIRCCommandTestCase):
@@ -233,7 +230,7 @@ class SDistTestCase(PyPIRCCommandTestCas
         f = open(join(self.tmp_dir, 'MANIFEST'))
         try:
             manifest = f.read()
-            self.assertEqual(manifest, MANIFEST % {'sep': os.sep})
+            self.assertEqual(manifest, MANIFEST)
         finally:
             f.close()
 
@@ -422,6 +419,56 @@ class SDistTestCase(PyPIRCCommandTestCas
 
         self.assertEqual(manifest, ['README.manual'])
 
+    def test_manifest_sep(self):
+        # paths in MANIFEST use '/' as path separator, so that Unix systems can
+        # read MANIFEST generated on Windows and vice versa (#828450)
+        self.addCleanup(setattr, os, 'sep', os.sep)
+        os.sep = '\\'
+
+        dist, cmd =  self.get_cmd()
+        cmd.ensure_finalized()
+        cmd.run()
+
+        expected = [
+            '# file GENERATED by distutils, do NOT edit\n',
+            'README\n',
+            'setup.py\n',
+            'somecode/__init__.py\n',
+        ]
+
+        f = open(cmd.manifest)
+        try:
+            manifest = f.readlines()
+        finally:
+            f.close()
+
+        self.assertEqual(manifest, expected)
+
+    def test_read_manifest(self):
+        # check if it's ok to read the MANIFEST file when all the file paths
+        # in it has taken '/' as separator, especially when Python use '\' as
+        # the separator on a specific system
+        self.addCleanup(setattr, os, 'sep', os.sep)
+        os.sep = '\\'
+
+        manifest = dedent("""\
+        README
+        setup.py
+        somecode/__init__.py
+        """)
+
+        f = open(join(self.tmp_dir, 'MANIFEST'), 'w')
+        try:
+            f.write(manifest)
+        finally:
+            f.close()
+
+        dist, cmd =  self.get_cmd()
+        cmd.ensure_finalized()
+        cmd.run()
+        self.assertEqual(cmd.filelist.files, manifest.splitlines())
+
+
 def test_suite():
     return unittest.makeSuite(SDistTestCase)