diff --git a/odoo/osv/expression.py b/odoo/osv/expression.py
index 35c66c7f923..927c7fa739c 100644
--- a/odoo/osv/expression.py
+++ b/odoo/osv/expression.py
@@ -441,14 +441,14 @@ def select_from_where(cr, select_field, from_table, where_field, where_ids, wher
     res = []
     if where_ids:
         if where_operator in ['<', '>', '>=', '<=']:
-            cr.execute('SELECT "%s" FROM "%s" WHERE "%s" %s %%s' % \
+            cr.execute('SELECT DISTINCT "%s" FROM "%s" WHERE "%s" %s %%s' % \
                 (select_field, from_table, where_field, where_operator),
                 (where_ids[0],))  # TODO shouldn't this be min/max(where_ids) ?
             res = [r[0] for r in cr.fetchall()]
         else:  # TODO where_operator is supposed to be 'in'? It is called with child_of...
             for i in range(0, len(where_ids), cr.IN_MAX):
                 subids = where_ids[i:i + cr.IN_MAX]
-                cr.execute('SELECT "%s" FROM "%s" WHERE "%s" IN %%s' % \
+                cr.execute('SELECT DISTINCT "%s" FROM "%s" WHERE "%s" IN %%s' % \
                     (select_field, from_table, where_field), (tuple(subids),))
                 res.extend([r[0] for r in cr.fetchall()])
     return res