Index: Lib/zipfile.py
===================================================================
--- Lib/zipfile.py	(revision 55850)
+++ Lib/zipfile.py	(working copy)
@@ -252,13 +252,29 @@
             self.extract_version = max(45, self.extract_version)
             self.create_version = max(45, self.extract_version)
 
+        filename, flag_bits = self._encodeFilenameFlags()
         header = struct.pack(structFileHeader, stringFileHeader,
-                 self.extract_version, self.reserved, self.flag_bits,
+                 self.extract_version, self.reserved, flag_bits,
                  self.compress_type, dostime, dosdate, CRC,
                  compress_size, file_size,
-                 len(self.filename), len(extra))
-        return header + self.filename + extra
+                 len(filename), len(extra))
+        return header + filename + extra
 
+    def _encodeFilenameFlags(self):
+        if isinstance(self.filename, unicode):
+            try:
+                return self.filename.encode('ascii'), self.flag_bits
+            except UnicodeEncodeError:
+                return self.filename.encode('utf-8'), self.flag_bits | 0x800
+        else:
+            return self.filename, self.flag_bits
+
+    def _decodeFilenameFlags(self):
+        if self.flag_bits & 0x800:
+            return self.filename.decode('utf-8'), self.flag_bits & ~0x800
+        else:
+            return self.filename, self.flag_bits
+
     def _decodeExtra(self):
         # Try to decode the extra field.
         extra = self.extra
@@ -684,6 +700,7 @@
 
             x._decodeExtra()
             x.header_offset = x.header_offset + concat
+            x.filename, x.flag_bits = x._decodeFilenameFlags()
             self.filelist.append(x)
             self.NameToInfo[x.filename] = x
             if self.debug > 2:
@@ -967,16 +984,17 @@
                     extract_version = zinfo.extract_version
                     create_version = zinfo.create_version
 
+                filename, flag_bits = zinfo._encodeFilenameFlags()
                 centdir = struct.pack(structCentralDir,
                   stringCentralDir, create_version,
                   zinfo.create_system, extract_version, zinfo.reserved,
-                  zinfo.flag_bits, zinfo.compress_type, dostime, dosdate,
+                  flag_bits, zinfo.compress_type, dostime, dosdate,
                   zinfo.CRC, compress_size, file_size,
-                  len(zinfo.filename), len(extra_data), len(zinfo.comment),
+                  len(filename), len(extra_data), len(zinfo.comment),
                   0, zinfo.internal_attr, zinfo.external_attr,
                   header_offset)
                 self.fp.write(centdir)
-                self.fp.write(zinfo.filename)
+                self.fp.write(filename)
                 self.fp.write(extra_data)
                 self.fp.write(zinfo.comment)
 
Index: Lib/test/test_zipfile.py
===================================================================
--- Lib/test/test_zipfile.py	(revision 55850)
+++ Lib/test/test_zipfile.py	(working copy)
@@ -515,6 +515,12 @@
         # and report that the first file in the archive was corrupt.
         self.assertRaises(RuntimeError, zipf.testzip)
 
+    def testUnicodeFilenames(self):
+        zf = zipfile.ZipFile(TESTFN, "w")
+        zf.writestr(u"foo.txt", "Test for unicode filename")
+        assert isinstance(zf.infolist()[0].filename, unicode)
+        zf.close()
+
     def tearDown(self):
         support.unlink(TESTFN)
         support.unlink(TESTFN2)