diff --git a/src/opserver/test-requirements.txt b/src/opserver/test-requirements.txt
index 9376030e977..4fb3300d902 100644
--- a/src/opserver/test-requirements.txt
+++ b/src/opserver/test-requirements.txt
@@ -9,6 +9,7 @@ flexmock==0.9.7
 kafka-python==0.9.2
 kazoo
 stevedore
+Cython==0.24.1
 cassandra-driver==3.0.0
 ../../../controller/src/analytics/test/utils/mockredis
 ../../../controller/src/analytics/test/utils/mockcassandra