diff --git a/stretch/preferences.d/entrouvert-debian-backports b/stretch/preferences.d/entrouvert-debian-backports
index 500b0f7..4f0e7af 100644
--- a/stretch/preferences.d/entrouvert-debian-backports
+++ b/stretch/preferences.d/entrouvert-debian-backports
@@ -10,6 +10,11 @@ Package: python-django-common
 Pin: release a=stretch-backports
 Pin-Priority: 900
 
+# python-attr >= 1.17 required for authentic
+Package: python-attr
+Pin: release a=stretch-backports
+Pin-Priority: 900
+
 #
 # certbot packages
 #