diff --git a/weboob/browser/filters/standard.py b/weboob/browser/filters/standard.py
index 4387bb1a..47b0cdec 100644
--- a/weboob/browser/filters/standard.py
+++ b/weboob/browser/filters/standard.py
@@ -636,7 +636,7 @@ class Time(Filter):
 
 class Duration(Time):
     klass = datetime.timedelta
-    regexp = re.compile(r'((?P<hh>\d+)[:;])?(?P<mm>\d+)[;:](?P<ss>\d+)')
+    _regexp = re.compile(r'((?P<hh>\d+)[:;])?(?P<mm>\d+)[;:](?P<ss>\d+)')
     kwargs = {'hours': 'hh', 'minutes': 'mm', 'seconds': 'ss'}