diff --git a/src/upbeat/api/orders.py b/src/upbeat/api/orders.py
index 038924f..a700bfe 100644
--- a/src/upbeat/api/orders.py
+++ b/src/upbeat/api/orders.py
@@ -235,12 +235,12 @@ def cancel_and_new(
         )
         return CancelAndNewOrderResponse.model_validate(response.data)
 
-    def get_chance(self, *, market: str) -> list[OrderChance]:
+    def get_chance(self, *, market: str) -> OrderChance:
         params = {"market": market}
         response = self._transport.request(
             "GET", "/v1/orders/chance", params=params, credentials=self._credentials
         )
-        return [OrderChance.model_validate(item) for item in response.data]
+        return OrderChance.model_validate(response.data)
 
 
 class AsyncOrdersAPI(_AsyncAPIResource):
@@ -458,9 +458,9 @@ async def cancel_and_new(
         )
         return CancelAndNewOrderResponse.model_validate(response.data)
 
-    async def get_chance(self, *, market: str) -> list[OrderChance]:
+    async def get_chance(self, *, market: str) -> OrderChance:
         params = {"market": market}
         response = await self._transport.request(
             "GET", "/v1/orders/chance", params=params, credentials=self._credentials
         )
-        return [OrderChance.model_validate(item) for item in response.data]
+        return OrderChance.model_validate(response.data)
diff --git a/src/upbeat/types/order.py b/src/upbeat/types/order.py
index 81375b8..1484cd4 100644
--- a/src/upbeat/types/order.py
+++ b/src/upbeat/types/order.py
@@ -32,7 +32,7 @@ class OrderCreated(BaseModel):
     state: str
     created_at: str
     volume: str | None = None
-    remaining_volume: str
+    remaining_volume: str | None = None
     executed_volume: str
     reserved_fee: str
     remaining_fee: str
@@ -42,8 +42,8 @@ class OrderCreated(BaseModel):
     time_in_force: str | None = None
     identifier: str | None = None
     smp_type: str | None = None
-    prevented_volume: str
-    prevented_locked: str
+    prevented_volume: str | None = None
+    prevented_locked: str | None = None
 
 
 # ── OrderDetail (GET /v1/order 응답) ────────────────────────────────────
diff --git a/tests/api/test_orders.py b/tests/api/test_orders.py
index 96935d9..e0cc632 100644
--- a/tests/api/test_orders.py
+++ b/tests/api/test_orders.py
@@ -512,27 +512,26 @@ def test_calls_correct_endpoint(self) -> None:
         def handler(request: httpx.Request) -> httpx.Response:
             assert request.url.path == "/v1/orders/chance"
             assert request.url.params["market"] == "KRW-BTC"
-            return _json_response([ORDER_CHANCE_DATA])
+            return _json_response(ORDER_CHANCE_DATA)
 
         transport = _make_transport(handler)
         api = OrdersAPI(transport, CREDENTIALS)
         result = api.get_chance(market="KRW-BTC")
-        assert len(result) == 1
-        assert isinstance(result[0], OrderChance)
-        assert result[0].bid_fee == "0.0005"
+        assert isinstance(result, OrderChance)
+        assert result.bid_fee == "0.0005"
 
     def test_parses_nested_objects(self) -> None:
         def handler(request: httpx.Request) -> httpx.Response:
-            return _json_response([ORDER_CHANCE_DATA])
+            return _json_response(ORDER_CHANCE_DATA)
 
         transport = _make_transport(handler)
         api = OrdersAPI(transport, CREDENTIALS)
         result = api.get_chance(market="KRW-BTC")
-        assert result[0].market.id == "KRW-BTC"
-        assert result[0].market.bid is not None
-        assert result[0].market.bid.currency == "KRW"
-        assert result[0].bid_account.currency == "KRW"
-        assert result[0].ask_account.currency == "BTC"
+        assert result.market.id == "KRW-BTC"
+        assert result.market.bid is not None
+        assert result.market.bid.currency == "KRW"
+        assert result.bid_account.currency == "KRW"
+        assert result.ask_account.currency == "BTC"
 
 
 # ── TestAsyncOrders ──────────────────────────────────────────────────────
@@ -578,10 +577,9 @@ async def handler(request: httpx.Request) -> httpx.Response:
     @pytest.mark.asyncio
     async def test_get_chance(self) -> None:
         async def handler(request: httpx.Request) -> httpx.Response:
-            return _json_response([ORDER_CHANCE_DATA])
+            return _json_response(ORDER_CHANCE_DATA)
 
         transport = _make_async_transport(handler)
         api = AsyncOrdersAPI(transport, CREDENTIALS)
         result = await api.get_chance(market="KRW-BTC")
-        assert len(result) == 1
-        assert isinstance(result[0], OrderChance)
+        assert isinstance(result, OrderChance)