diff --git a/Lib/xmlrpclib.py b/Lib/xmlrpclib.py
index 2da17c4..abd1a07 100644
--- a/Lib/xmlrpclib.py
+++ b/Lib/xmlrpclib.py
@@ -1118,7 +1118,7 @@
             raise ProtocolError(
                 host + handler,
                 resp.status, resp.reason,
-                resp.getheaders()
+                dict(resp.getheaders())
                 )
 
         self.verbose = verbose