diff --git a/transmission/config.json b/transmission/config.json
index 0a121e420..b4f948e08 100644
--- a/transmission/config.json
+++ b/transmission/config.json
@@ -50,7 +50,7 @@
     "PGID": "int",
     "TZ": "str?",
     "download_dir": "str",
-    "incomplete_dir": "str",
+    "incomplete_dir": "str?",
     "localdisks": ["str?"],
     "networkdisks": "str?",
     "cifsusername": "str?",