diff --git a/requests/models.py b/requests/models.py
index 8d33c32b..098098eb 100644
--- a/requests/models.py
+++ b/requests/models.py
@@ -371,7 +371,13 @@ class Request(object):
                     fields = dict(self.data)
 
                 for (k, v) in self.files.items():
-                    fields.update({k: (guess_filename(k) or k, v.read())})
+                    # support for explicit filename
+                    if isinstance(v, (tuple, list)):
+                        fn, fp = v
+                    else:
+                        fn = guess_filename(v) or k
+                        fp = v
+                    fields.update({k: (fn, fp.read())})
 
                 (body, content_type) = encode_multipart_formdata(fields)
             else:
@@ -425,7 +431,7 @@ class Request(object):
                         c[k] = v
 
                     # Turn it into a header.
-                    cookie_header = c.output(header='').strip()
+                    cookie_header = c.output(header='', sep='; ').strip()
 
                     # Attach Cookie header to request.
                     self.headers['Cookie'] = cookie_header