Index: Lib/httplib.py
===================================================================
--- Lib/httplib.py	(revision 73751)
+++ Lib/httplib.py	(working copy)
@@ -865,6 +865,10 @@
                         host_enc = self.host.encode("ascii")
                     except UnicodeEncodeError:
                         host_enc = self.host.encode("idna")
+                    # As per RFC 2732, IPv6 address should be wrapped
+                    # with [] to use as Host header
+                    if host_enc.find(':') >= 0:
+                        host_enc = "[" + host_enc + "]"
                     if self.port == self.default_port:
                         self.putheader('Host', host_enc)
                     else: