diff --git a/mdcms.py b/mdcms.py
index 0a72de2..62ee3a6 100644
--- a/mdcms.py
+++ b/mdcms.py
@@ -108,9 +108,10 @@ def read_config(site_path: Path) -> dict:
 def get_category_info(cfg: dict) -> dict:
     use = str(cfg.get("categories-use", "no")).lower() in ("yes", "true")
     default_cat = cfg.get("default-category") or {}
-    default_code = default_cat.get("code") if isinstance(default_cat, dict) else None
+    raw_default = default_cat.get("code") if isinstance(default_cat, dict) else None
+    default_code = str(raw_default) if raw_default is not None else None
     cats = cfg.get("categories") or []
-    codes = [c["code"] for c in cats if isinstance(c, dict) and "code" in c]
+    codes = [str(c["code"]) for c in cats if isinstance(c, dict) and "code" in c]
     return {"use": use, "default_code": default_code, "codes": codes}