diff --git a/backend/address2UPRN/main.py b/backend/address2UPRN/main.py
index a7378fbe..6b684cef 100644
--- a/backend/address2UPRN/main.py
+++ b/backend/address2UPRN/main.py
@@ -60,7 +60,7 @@ def get_uprn_from_historic_epc(
     except FileNotFoundError:
         return None
 
-    uprn = result.unambiguous_uprn()
+    uprn: Optional[str] = result.unambiguous_uprn()
     if not uprn or uprn in ("", "nan"):
         return None
 
diff --git a/scripts/historic_epc_demo.py b/scripts/historic_epc_demo.py
index b47c3a3c..31e1ee28 100644
--- a/scripts/historic_epc_demo.py
+++ b/scripts/historic_epc_demo.py
@@ -12,6 +12,7 @@ Usage:
 import sys
 
 from datatypes.epc.domain.historic_epc_matching import match_addresses_for_postcode
+from typing import Optional
 
 
 def main(user_address: str, postcode: str) -> None:
@@ -29,7 +30,7 @@ def main(user_address: str, postcode: str) -> None:
         )
 
     print()
-    uprn = result.unambiguous_uprn()
+    uprn: Optional[str] = result.unambiguous_uprn()
     if uprn:
         print(f"Unambiguous UPRN: {uprn}")
     else: