Guard the chmod in case external_attr is 0.

1 files changed, 3 insertions, 1 deletions

diff --git a/setuptools/archive_util.py b/setuptools/archive_util.py
index 8ad14752..e22b25c0 100755
--- a/setuptools/archive_util.py
+++ b/setuptools/archive_util.py
@@ -158,7 +158,9 @@ def unpack_zipfile(filename, extract_dir, progress_filter=default_filter):
                 finally:
                     f.close()
                     del data
-            os.chmod(target, info.external_attr >> 16)
+            unix_attributes = info.external_attr >> 16
+            if unix_attributes:
+                os.chmod(target, unix_attributes)
     finally:
         z.close()