diff --git a/requirements.txt b/requirements.txt
index 47fa77580..92e8b0b0f 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -19,7 +19,7 @@ gunicorn==19.6.0
 docopt==0.6.2
 six==1.10.0
 iso8601==0.1.12
-celery==3.1.25
+celery==3.1.25 # pyup: <4
 
 # pin to minor version 3.1.x
 notifications-python-client>=3.1,<3.2