diff --git a/src/ukify/ukify.py b/src/ukify/ukify.py
index 8324942f992..cf7db49bdd1 100755
--- a/src/ukify/ukify.py
+++ b/src/ukify/ukify.py
@@ -1016,6 +1016,8 @@ class ConfigItem:
         assert not group
 
         old = getattr(namespace, dest, [])
+        if old is None:
+            old = []
         setattr(namespace, dest, value + old)
 
     @staticmethod