diff --git a/django_lostplaces/lostplaces/forms.py b/django_lostplaces/lostplaces/forms.py
index 86f291c..17e51cc 100644
--- a/django_lostplaces/lostplaces/forms.py
+++ b/django_lostplaces/lostplaces/forms.py
@@ -26,6 +26,10 @@ class ExplorerCreationForm(UserCreationForm):
             self.add_error('voucher', 'Invalid voucher')
             return False
 
+        if not submitted_voucher.valid:
+            self.add_error('voucher', 'Expired voucher')
+            return False
+
         fetched_voucher.delete()
         return True