diff --git a/opentech/apply/users/management/commands/migrate_users.py b/opentech/apply/users/management/commands/migrate_users.py
index 5db04a85b891422cb4bf442706e563d4cd143550..3e09f41605ca237beb1b9ff8e6459302fa4abdc5 100644
--- a/opentech/apply/users/management/commands/migrate_users.py
+++ b/opentech/apply/users/management/commands/migrate_users.py
@@ -84,7 +84,8 @@ class Command(BaseCommand):
         if not anonymize or self.is_staff(email):
             return email
 
-        return "aeon+%s@torchbox.com" % user['uid']
+        uid = user['uid']
+        return f"aeon+{uid}@torchbox.com"
 
     def is_staff(self, email):
         _, email_domain = email.split('@')