diff --git a/mandaye/http.py b/mandaye/http.py
index d2855dd..fd70920 100644
--- a/mandaye/http.py
+++ b/mandaye/http.py
@@ -154,6 +154,10 @@ class HTTPResponse(object):
         self.headers.load_httpmessage(response.headers)
         for setcookie in response.headers.getheaders('set-cookie'):
             try:
+                # WARNING hack for biblio.vincennes.fr
+                # during a basic login we have two set-coookie with the same key
+                # SimpleCookie will merge the 2 set-cookies by default
+                # this hack force to keep the second Set-cookie only
                 cookie = Cookie.SimpleCookie("Set-Cookie: %s" % setcookie)
                 cookie = cookie.values()[0]
                 if self.cookies.has_key(cookie.key):