diff --git a/requirements.txt b/requirements.txt
index 6c761f771..63ca047ad 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -6,6 +6,7 @@ credstash==1.8.0
 boto3==1.3.0
 Pygments==2.0.2
 py-gfm==0.1.2
+blinker==1.4
 
 git+https://github.com/alphagov/notifications-python-client.git@0.5.0#egg=notifications-python-client==0.5.0