diff --git a/requests/models.py b/requests/models.py
index 0d7b67cb..7690f16a 100644
--- a/requests/models.py
+++ b/requests/models.py
@@ -230,7 +230,8 @@ class Request(object):
 
                 # Facilitate non-RFC2616-compliant 'location' headers
                 # (e.g. '/path/to/resource' instead of 'http://domain.tld/path/to/resource')
-                url = urljoin(r.url, urllib.quote(urllib.unquote(url)))
+                if not urlparse(url).netloc:
+                    url = urljoin(r.url, urllib.quote(urllib.unquote(url)))
 
                 # http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.3.4
                 if r.status_code is 303: