--- a/src/pyams_utils/fanstatic.py	Fri Nov 23 09:34:34 2018 +0100
+++ b/src/pyams_utils/fanstatic.py	Fri Nov 30 12:03:59 2018 +0100
@@ -28,6 +28,8 @@
 class ExternalResource(Resource):
     """Fanstatic external resource"""
 
+    dependency_nr = 0
+
     def __init__(self, library, path, defer=False, resource_type=None, **kwargs):
         set_resource_file_existence_checking(False)
         try: