diff --git a/nonebot/drivers/aiohttp.py b/nonebot/drivers/aiohttp.py
index b12d204b..6b437e22 100644
--- a/nonebot/drivers/aiohttp.py
+++ b/nonebot/drivers/aiohttp.py
@@ -124,6 +124,8 @@ class Session(HTTPClientSession):
 
     @override
     async def setup(self) -> None:
+        if self._client is not None:
+            raise RuntimeError("Session has already been initialized")
         self._client = aiohttp.ClientSession(
             cookies=self._cookies,
             headers=self._headers,
diff --git a/nonebot/drivers/httpx.py b/nonebot/drivers/httpx.py
index 8300323b..68eed464 100644
--- a/nonebot/drivers/httpx.py
+++ b/nonebot/drivers/httpx.py
@@ -93,6 +93,8 @@ class Session(HTTPClientSession):
 
     @override
     async def setup(self) -> None:
+        if self._client is not None:
+            raise RuntimeError("Session has already been initialized")
         self._client = httpx.AsyncClient(
             params=self._params,
             headers=self._headers,
diff --git a/tests/test_driver.py b/tests/test_driver.py
index 546cfeec..636e02c3 100644
--- a/tests/test_driver.py
+++ b/tests/test_driver.py
@@ -328,6 +328,11 @@ async def test_http_client_session(driver: Driver, server_url: URL):
     with pytest.raises(RuntimeError):
         await session.request(request)
 
+    with pytest.raises(RuntimeError):  # noqa: PT012
+        async with session:
+            async with session:
+                ...
+
     async with session as session:
         # simple post with query, headers, cookies and content
         request = Request(