diff --git a/src/calibre/utils/zipfile.py b/src/calibre/utils/zipfile.py
index dbcc125274..5c19444bd6 100644
--- a/src/calibre/utils/zipfile.py
+++ b/src/calibre/utils/zipfile.py
@@ -1227,7 +1227,7 @@ class ZipFile:
         self.fp.flush()
         if zinfo.flag_bits & 0x08:
             # Write CRC and file sizes after the file data
-            self.fp.write(struct.pack("<lLL", zinfo.CRC, zinfo.compress_size,
+            self.fp.write(struct.pack("<LLL", zinfo.CRC, zinfo.compress_size,
                   zinfo.file_size))
         self.filelist.append(zinfo)
         self.NameToInfo[zinfo.filename] = zinfo