Index: Lib/urllib/request.py
===================================================================
--- Lib/urllib/request.py	(revision 65739)
+++ Lib/urllib/request.py	(working copy)
@@ -100,7 +100,7 @@
 from urllib.parse import (
     urlparse, urlsplit, urljoin, unwrap, quote, unquote,
     splittype, splithost, splitport, splituser, splitpasswd,
-    splitattr, splitquery, splitvalue, to_bytes)
+    splitattr, splitquery, splitvalue, to_bytes, fix_broken)
 from urllib.response import addinfourl, addclosehook
 
 # check for SSL
@@ -535,8 +535,11 @@
             newurl = headers["uri"]
         else:
             return
-        newurl = urljoin(req.get_full_url(), newurl)
 
+        # fix the broken url and then join with req.get_full_url()
+        newurl = urljoin(req.get_full_url(), 
+                    fix_broken(newurl))
+
         # XXX Probably want to forget about the state of the current
         # request, although that might interact poorly with other
         # handlers that also use handler-specific request attributes
Index: Lib/urllib/parse.py
===================================================================
--- Lib/urllib/parse.py	(revision 65739)
+++ Lib/urllib/parse.py	(working copy)
@@ -41,6 +41,13 @@
     """Clear the parse cache."""
     _parse_cache.clear()
 
+def fix_broken(url):
+    """Attempt to fix broken, non-confirming urls. Handle the way the browsers
+    handle it."""
+    scheme, netloc, path, params, query, fragment = urlparse(url)
+    if not path: path = '/'
+    fixedurl = urlunparse((scheme, netloc, path, params, query, fragment))
+    return fixedurl
 
 class ResultMixin(object):
     """Shared methods for the parsed result objects."""