diff --git a/radicale/config.py b/radicale/config.py
index 413b0dfa..24899190 100644
--- a/radicale/config.py
+++ b/radicale/config.py
@@ -607,7 +607,7 @@ DEFAULT_CONFIG_SCHEMA: types.CONFIG_SCHEMA = OrderedDict([
             "help": "conversion bday alarm trigger template",
             "type": str}),
         ("conversion_bday_age_max", {
-            "value": 99,
+            "value": "99",
             "help": "conversion bday age max",
             "type": positive_int}),
         ])),