diff --git a/door.py b/door.py
index 4751437..b3f6204 100644
--- a/door.py
+++ b/door.py
@@ -85,6 +85,8 @@ def read_valid_tokens():
                     try:
                         if len(valid_thru.strip()) > 0:
                             valid_thru = datetime.date.fromisoformat(valid_thru)
+                        else:
+                            valid_thru = None
                     except Exception:
                         log(f"Could not parse valid thru date for token {token} in line {i}")
                         valid_thru = None