Index: django/db/models/fields/related.py
===================================================================
--- django/db/models/fields/related.py	(revision 8255)
+++ django/db/models/fields/related.py	(working copy)
@@ -147,7 +147,7 @@
         if hasattr(value, 'as_sql'):
             sql, params = value.as_sql()
             return QueryWrapper(('(%s)' % sql), params)
-        if lookup_type == 'exact':
+        if lookup_type in ['exact', 'gt', 'lt']:
             return [pk_trace(value)]
         if lookup_type == 'in':
             return [pk_trace(v) for v in value]