diff --git a/muk_fields_lobject/controllers/main.py b/muk_fields_lobject/controllers/main.py
index 7b2f6b5..9ec1ec7 100644
--- a/muk_fields_lobject/controllers/main.py
+++ b/muk_fields_lobject/controllers/main.py
@@ -54,7 +54,7 @@ class LargeObjectController(http.Controller):
         elif id and model in request.env.registry:
             obj = request.env[model].browse(int(id))
         if not obj or not obj.exists() or field not in obj:
-            _logger.info(not obj, not obj.exists(), field not in obj)
+            _logger.info(str(not obj), str(not obj.exists()), str(field not in obj))
             return request.not_found()
         try:
             last_update = obj['__last_update']