diff --git a/requirements.txt b/requirements.txt
index 2ce5add5e..a414d2549 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -20,7 +20,8 @@ statsd==3.2.1
 jsonschema==2.5.1
 Flask-Redis==0.1.0
 
-notifications-python-client==3.0.0
+# pin to minor version 3.1.x
+notifications-python-client>=3.1,<3.2
 
 git+https://github.com/alphagov/notifications-utils.git@12.2.0#egg=notifications-utils==12.2.0