-

diff --git a/django/db/models/query.py b/django/db/models/query.py
index 836d394..3b60aa6 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -48,6 +48,12 @@ class QuerySet(object):
     """
 
     def __init__(self, model=None, query=None, using=None):
+        if hasattr(model, 'all'):
+            queryset = model.all()
+            model = queryset.model
+            query = queryset.query
+            using = queryset.using
+
         self.model = model
         self._db = using
         self.query = query or sql.Query(self.model)