diff --git a/db_logic/medicament.py b/db_logic/medicament.py
index 03a94a0..64f836c 100644
--- a/db_logic/medicament.py
+++ b/db_logic/medicament.py
@@ -970,7 +970,7 @@ class BllMedicament(Repository):
         add_year = int(medicament_variety_obj.remark5) if medicament_variety_obj.remark5 else 1
         date_now = datetime.datetime.now()
         add_expiration_date = (date_now + relativedelta(years=add_year)).strftime("%Y-%m-%d %H:%M:%S")
-        if add_expiration_date > drug_entry.expiration_date:
+        if not drug_entry.expiration_date or add_expiration_date > str(drug_entry.expiration_date):
             return
         else:
             drug_entry.expiration_date = add_expiration_date