diff -r 6531c7a99496 django/db/models/manipulators.py
--- a/django/db/models/manipulators.py	Sun Mar 09 21:59:00 2008 +0000
+++ b/django/db/models/manipulators.py	Sun Mar 09 19:14:48 2008 -0500
@@ -124,8 +124,9 @@ class AutomaticManipulator(oldforms.Mani
                     else:
                         new_vals = new_data.getlist(f.name)
                     # First, clear the existing values.
-                    rel_manager = getattr(new_object, f.name)
-                    rel_manager.clear()
+                    if self.change:
+                        rel_manager = getattr(new_object, f.name)
+                        rel_manager.clear()
                     # Then, set the new values.
                     for n in new_vals:
                         rel_manager.add(f.rel.to._default_manager.get(pk=n))