diff --git a/passbook/policies/process.py b/passbook/policies/process.py
index 50cd4c1bd..64ccf4962 100644
--- a/passbook/policies/process.py
+++ b/passbook/policies/process.py
@@ -1,6 +1,7 @@
 """passbook policy task"""
 from multiprocessing import Process
 from multiprocessing.connection import Connection
+from typing import Optional
 
 from django.core.cache import cache
 from structlog import get_logger
@@ -12,7 +13,7 @@ from passbook.policies.types import PolicyRequest, PolicyResult
 LOGGER = get_logger()
 
 
-def cache_key(policy: Policy, user: User = None) -> str:
+def cache_key(policy: Policy, user: Optional[User] = None) -> str:
     """Generate Cache key for policy"""
     prefix = f"policy_{policy.pk}"
     if user:
diff --git a/passbook/providers/saml/utils/time.py b/passbook/providers/saml/utils/time.py
index 3e88e0d93..2fe490ba9 100644
--- a/passbook/providers/saml/utils/time.py
+++ b/passbook/providers/saml/utils/time.py
@@ -1,5 +1,6 @@
 """Time utilities"""
 import datetime
+from typing import Optional
 
 from django.core.exceptions import ValidationError
 from django.utils.translation import gettext_lazy as _
@@ -38,7 +39,7 @@ def timedelta_from_string(expr: str) -> datetime.timedelta:
     return datetime.timedelta(**kwargs)
 
 
-def get_time_string(delta: datetime.timedelta = None) -> str:
+def get_time_string(delta: Optional[datetime.timedelta] = None) -> str:
     """Get Data formatted in SAML format"""
     if delta is None:
         delta = datetime.timedelta()