diff --git a/uarite/core.py b/uarite/core.py
index fd8376a..983cc0e 100644
--- a/uarite/core.py
+++ b/uarite/core.py
@@ -154,7 +154,7 @@ def model_name(model: str) -> str:
 
 
 @lru_cache(maxsize=1024)
-def uaparse(ua: str) -> UA:
+def uaparse(ua: str | None) -> UA:
     """Parse a User-Agent string into a compact ``UA`` record.
 
     ``pretty`` is "" for empty/missing UAs and the original string when