diff --git a/weboob/tools/application/base.py b/weboob/tools/application/base.py
index 0f19cf82..8fce3c89 100644
--- a/weboob/tools/application/base.py
+++ b/weboob/tools/application/base.py
@@ -26,7 +26,7 @@ import sys
 import tempfile
 import warnings
 
-from weboob.capabilities.base import ConversionWarning
+from weboob.capabilities.base import ConversionWarning, CapBaseObject
 from weboob.tools.browser.browser import FormFieldConversionWarning
 from weboob.core import Weboob, CallErrors
 from weboob.core.backendscfg import BackendsConfig
@@ -250,6 +250,8 @@ class BaseApplication(object):
     def _do_complete_obj(self, backend, fields, obj):
         if not obj:
             return obj
+        if not isinstance(obj, CapBaseObject):
+            return obj
 
         obj.backend = backend.name
         if fields is None or len(fields) > 0: