diff --git a/src/commons/addr/geo.py b/src/commons/addr/geo.py
index 4d11443..fab1ddf 100644
--- a/src/commons/addr/geo.py
+++ b/src/commons/addr/geo.py
@@ -58,9 +58,13 @@ def _parse_ipify(data: dict) -> Optional[str]:
     return ip or None
 
 
-def _state_slug(state: str) -> str:
-    """lowercase ascii-folded state slug with underscores (e.g. 'New York' -> 'new_york')"""
-    folded = unicodedata.normalize("NFKD", state).encode("ascii", "ignore").decode("ascii")
+def _state_slug(state) -> str:
+    """lowercase ascii-folded state slug with underscores (e.g. 'New York' -> 'new_york')
+
+    coerces to str first so a malformed non-string `state` doesn't raise TypeError out
+    of unicodedata.normalize and break the 'None on any parse failure' contract.
+    """
+    folded = unicodedata.normalize("NFKD", str(state)).encode("ascii", "ignore").decode("ascii")
     return folded.lower().replace(" ", "_")