diff --git a/Lib/zipfile.py b/Lib/zipfile.py
index 2819f1b..5c3fff3 100644
--- a/Lib/zipfile.py
+++ b/Lib/zipfile.py
@@ -664,7 +664,7 @@
 
                 if zinfo.header_offset > ZIP64_LIMIT:
                     extra.append(zinfo.header_offset)
-                    header_offset = 0xffffffff #-1
+                    header_offset = -1  # struct "l" format:  32 one bits
                 else:
                     header_offset = zinfo.header_offset