diff --git a/src/enablebanking_sdk/service/integration.py b/src/enablebanking_sdk/service/integration.py
index 08644b1..0a6414a 100644
--- a/src/enablebanking_sdk/service/integration.py
+++ b/src/enablebanking_sdk/service/integration.py
@@ -1,6 +1,6 @@
 import logging
 from datetime import datetime, timedelta
-from typing import Optional, Tuple
+from typing import Tuple
 from requests.exceptions import HTTPError
 
 import jwt
@@ -15,7 +15,7 @@
 
 class EnableBankingIntegration:
     token: str
-    token_expiration: Optional[datetime] = None
+    token_expiration: datetime | None = None
 
     base_url: str
     app_id: str
@@ -121,7 +121,7 @@ def start_user_session(self, request: dict) -> dict:
             json=request,
         )
 
-    def delete_user_session(self, session_id: str, psu_headers: dict):
+    def delete_user_session(self, session_id: str, psu_headers: dict | None = None):
         return self._request(
             method="DELETE",
             path=f"/sessions/{session_id}",
@@ -144,7 +144,7 @@ def get_account_transactions(
         psu_headers: dict | None = None,
         continuation_key: str | None = None,
     ) -> dict:
-        def _fmt_dt(date: Optional[datetime]) -> Optional[str]:
+        def _fmt_dt(date: datetime | None) -> str | None:
             return date.replace(tzinfo=None).strftime("%Y-%m-%d") if date else None
 
         return self._request(
@@ -162,7 +162,7 @@ def _fmt_dt(date: Optional[datetime]) -> Optional[str]:
     def get_account_balances(
         self,
         account_uid: str,
-        psu_headers: Optional[dict] = None,
+        psu_headers: dict | None = None,
     ) -> dict:
         return self._request(
             method="GET",