diff --git a/teuthology/task/rbd.py b/teuthology/task/rbd.py
index 66500c03f33..c3cf0958fb0 100644
--- a/teuthology/task/rbd.py
+++ b/teuthology/task/rbd.py
@@ -355,6 +355,8 @@ def task(ctx, config):
     if isinstance(config, dict):
         role_images = {}
         for role, properties in config.iteritems():
+            if properties is None:
+                properties = {}
             role_images[role] = properties.get('image_name')
     else:
         role_images = config