diff --git a/requirements.txt b/requirements.txt
index 8cc8a0e8018f98d56ba84fdda652438860425582..c77486972401e2f8d83752c763f4e359607c64e8 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -68,6 +68,10 @@ ipaddress
 # 4.6.5 causes a 403 on /saml2/acs upon sign in with djangosaml2
 pysaml2==4.6.0
 djangosaml2==0.17.2
+
+# Try to avoid https://github.com/Julian/jsonschema/issues/449
+attrs>=19
+
 python-memcached
 
 # }}}