diff --git a/zipstream/__init__.py b/zipstream/__init__.py
index 60dbef2..4f9d7be 100644
--- a/zipstream/__init__.py
+++ b/zipstream/__init__.py
@@ -262,7 +262,10 @@ def __write(self, filename=None, iterable=None, arcname=None, compress_type=None
         else:
             zinfo.compress_type = compress_type
 
-        zinfo.file_size = 0
+        if st:
+            zinfo.file_size = st[6]
+        else:
+            zinfo.file_size = 0
         zinfo.flag_bits = 0x00
         zinfo.flag_bits |= 0x08                 # ZIP flag bits, bit 3 indicates presence of data descriptor
         zinfo.header_offset = self.fp.tell()    # Start of header bytes