diff --git a/cloudinit/config/cc_disk_setup.py b/cloudinit/config/cc_disk_setup.py
index efa7a22..eac8afe 100644
--- a/cloudinit/config/cc_disk_setup.py
+++ b/cloudinit/config/cc_disk_setup.py
@@ -213,7 +213,7 @@ def update_fs_setup_devices(disk_setup, tformer):
 
         if part and 'partition' in definition:
             definition['_partition'] = definition['partition']
-        definition['partition'] = part
+            definition['partition'] = part
 
 
 def value_splitter(values, start=None):