diff --git a/weboob/tools/value.py b/weboob/tools/value.py
index 31ecdef1cc31ec845844d3df6e45b550d111a93a..5c479b78034dd95898858108e6e8aa72471ae674 100644
--- a/weboob/tools/value.py
+++ b/weboob/tools/value.py
@@ -151,9 +151,9 @@ def get(self):
 
 class ValueTransient(Value):
     def __init__(self, *args, **kwargs):
-        kwargs['transient'] = True
-        kwargs['default'] = None
-        kwargs['required'] = False
+        kwargs.setdefault('transient', True)
+        kwargs.setdefault('default', '')
+        kwargs.setdefault('required', False)
         super(ValueTransient, self).__init__(*args, **kwargs)
 
     def dump(self):