diff --git a/wlauto/utils/types.py b/wlauto/utils/types.py
index e9a49fb9..66c97998 100644
--- a/wlauto/utils/types.py
+++ b/wlauto/utils/types.py
@@ -169,7 +169,7 @@ def list_or_string(value):
         return [value]
     else:
         try:
-            return list(value)
+            return map(str, value)
         except ValueError:
             return [str(value)]