diff --git a/containers/xos/pip_requirements.txt b/containers/xos/pip_requirements.txt
index 00be225..6ab4271 100644
--- a/containers/xos/pip_requirements.txt
+++ b/containers/xos/pip_requirements.txt
@@ -100,6 +100,7 @@
 pbr==1.10.0
 pika==0.10.0
 pika-pool==0.1.3
+ply==3.10
 positional==1.1.1
 prettytable==0.7.2
 protobuf==3.2.0