diff --git a/distlib/util.py b/distlib/util.py
index dd01849..d1ec58a 100644
--- a/distlib/util.py
+++ b/distlib/util.py
@@ -1435,7 +1435,7 @@ def connect(self):
             context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
             if hasattr(ssl, 'OP_NO_SSLv2'):
                 context.options |= ssl.OP_NO_SSLv2
-            if self.cert_file:
+            if hasattr(self, 'cert_file') and self.cert_file:
                 context.load_cert_chain(self.cert_file, self.key_file)
             kwargs = {}
             if self.ca_certs: