Index: django/db/models/query.py
===================================================================
--- django/db/models/query.py   (revision 6891)
+++ django/db/models/query.py   (working copy)
@@ -546,6 +546,9 @@
                 if "." in col_name:
                     table_prefix, col_name = col_name.split('.', 1)
                     table_prefix = qn(table_prefix) + '.'
+                   if col_name.startswith('-'):
+                       col_name = col_name[1:]
+                       order = "DESC"
                 else:
                     # Use the database table as a column prefix if it wasn't given,
                     # and if the requested column isn't a custom SELECT.