diff --git a/Lib/xml/sax/saxutils.py b/Lib/xml/sax/saxutils.py
index 5d784bd..83c779f 100644
--- a/Lib/xml/sax/saxutils.py
+++ b/Lib/xml/sax/saxutils.py
@@ -218,7 +218,7 @@
         source = xmlreader.InputSource()
         source.setByteStream(f)
         if hasattr(f, "name"):
-            f.setSystemId(f.name)
+            source.setSystemId(f.name)
 
     if source.getByteStream() is None:
         sysid = source.getSystemId()