Index: Lib/zipfile.py
===================================================================
--- Lib/zipfile.py	(revision 42155)
+++ Lib/zipfile.py	(working copy)
@@ -63,6 +63,18 @@
 _FH_FILENAME_LENGTH = 10
 _FH_EXTRA_FIELD_LENGTH = 11
 
+# Mapping of os.name values to create_system values
+_PKWARE_SYSTEMS=dict(
+        nt=0,
+        posix=3,
+        mac=7,
+        os2=0,
+        ce=0,
+        java=0,
+        riscos=13,
+)
+
+
 def is_zipfile(filename):
     """Quickly see if file is a ZIP file by checking the magic number."""
     try:
@@ -131,7 +143,11 @@
         self.compress_type = ZIP_STORED # Type of compression for the file
         self.comment = ""               # Comment for each file
         self.extra = ""                 # ZIP extra data
-        self.create_system = 0          # System which created ZIP archive
+        try:
+            self.create_system = _PKWARE_SYSTEMS[os.name]
+        except KeyError:
+            self.create_system = 0 # default to MS-DOS
+
         self.create_version = 20        # Version which created ZIP archive
         self.extract_version = 20       # Version needed to extract archive
         self.reserved = 0               # Must be zero