diff --git a/cschwabpy/models/__init__.py b/cschwabpy/models/__init__.py
index 29d6f84..6459efa 100644
--- a/cschwabpy/models/__init__.py
+++ b/cschwabpy/models/__init__.py
@@ -203,7 +203,7 @@ class Market(JSONSerializableBaseModel):
     product: str
     productName: str
     isOpen: bool
-    sessionHours: SessionHours
+    sessionHours: Optional[SessionHours] = None
 
 
 class EquityMarket(JSONSerializableBaseModel):
diff --git a/tests/test_models.py b/tests/test_models.py
index de566ad..d20ee5b 100644
--- a/tests/test_models.py
+++ b/tests/test_models.py
@@ -97,6 +97,7 @@ async def test_market_hours(httpx_mock: HTTPXMock) -> None:
     all_market = MarketHourInfo(**all_market_json)
     assert all_market is not None
     assert all_market.equity is not None
+    assert all_market.equity.EQ.sessionHours is not None
     assert all_market.equity.EQ.sessionHours.regularMarket is not None
     assert all_market.equity.EQ.sessionHours.preMarket is not None