diff --git a/bin/addons/base/ir/ir_attachment.py b/bin/addons/base/ir/ir_attachment.py
index ca34404be01..dd1934de698 100644
--- a/bin/addons/base/ir/ir_attachment.py
+++ b/bin/addons/base/ir/ir_attachment.py
@@ -48,11 +48,12 @@ class ir_attachment(osv.osv):
         cache = {}
         ima = self.pool.get('ir.model.access')
         for m in models:
-            if m['res_model'] not in cache:
-                cache[m['res_model']] = ima.check(cr, uid, m['res_model'], 'read',
-                                                  raise_exception=False)
-            if not cache[m['res_model']]:
-                ids.remove(m['id'])
+            if m['res_model']:
+                if m['res_model'] not in cache:
+                    cache[m['res_model']] = ima.check(cr, uid, m['res_model'], 'read',
+                                                      raise_exception=False)
+                if not cache[m['res_model']]:
+                    ids.remove(m['id'])
 
         if count:
             return len(ids)