diff --git a/src/pybind/ceph_volume_client.py b/src/pybind/ceph_volume_client.py
index 67f3a689ad9..cfd54a5d172 100644
--- a/src/pybind/ceph_volume_client.py
+++ b/src/pybind/ceph_volume_client.py
@@ -28,6 +28,8 @@ def to_bytes(param):
     '''
     if isinstance(param, str):
         return param.encode('utf-8')
+    elif param is None:
+        return param
     else:
         return str(param).encode('utf-8')