diff --git a/combo_plugin_gnm/templatetags/gnm.py b/combo_plugin_gnm/templatetags/gnm.py
index d918770..d82c2d0 100644
--- a/combo_plugin_gnm/templatetags/gnm.py
+++ b/combo_plugin_gnm/templatetags/gnm.py
@@ -279,6 +279,7 @@ def get_mairie_opening_hours(mairie_data):
         previous_week = base_datetime - datetime.timedelta(7)
         next_week = base_datetime + datetime.timedelta(7)
         for specification in mairie_data.get('openinghoursspecification', []):
+            known_format = True
             valid_from, valid_through = previous_week, next_week
             if specification.get('validFrom'):
                 valid_from = parse_valid_from(specification)
@@ -304,8 +305,12 @@ def get_mairie_opening_hours(mairie_data):
 
     if not (any([x['am'] for x in opening_hours_dict.values()]) or
             any([x['pm'] for x in opening_hours_dict.values()])):
-        # always closed, return None to mark unavailability
-        return None
+        # always closed, returns None if the format is unknown so it can be
+        # displayed as "unavailable".
+        if not known_format:
+            return None
+        # otherwise returns an array of closed days
+        return [(weekday, {'am': None, 'pm': ''}) for weekday in FR_WEEKDAYS]
 
     return [
             (FR_ABBREV_WEEKDAYS_LIST[weekday], hours) for weekday, hours in opening_hours_dict.items()