diff --git a/aiohttp/web_fileresponse.py b/aiohttp/web_fileresponse.py
index 921741e8ef5..da023660ada 100644
--- a/aiohttp/web_fileresponse.py
+++ b/aiohttp/web_fileresponse.py
@@ -128,7 +128,8 @@ async def _sendfile(
 
         loop = request._loop
         transport = request.transport
-        assert transport is not None
+        if transport is None:
+            raise RuntimeError("Transport is not available")
 
         try:
             await loop.sendfile(transport, fobj, offset, count)
diff --git a/aiohttp/web_ws.py b/aiohttp/web_ws.py
index 8eee7e3ad71..1919c000f70 100644
--- a/aiohttp/web_ws.py
+++ b/aiohttp/web_ws.py
@@ -317,7 +317,8 @@ def _pre_start(self, request: BaseRequest) -> tuple[str | None, WebSocketWriter]
         self.force_close()
         self._compress = compress
         transport = request._protocol.transport
-        assert transport is not None
+        if transport is None:
+            raise RuntimeError("Transport is not available")
         writer = WebSocketWriter(
             request._protocol,
             transport,
diff --git a/tests/test_web_websocket.py b/tests/test_web_websocket.py
index 33380d94560..6ca8caebfb8 100644
--- a/tests/test_web_websocket.py
+++ b/tests/test_web_websocket.py
@@ -671,3 +671,12 @@ async def test_get_extra_info(
     ws._writer = ws_transport
 
     assert expected_result == ws.get_extra_info(valid_key, default_value)
+
+
+async def test_prepare_transport_not_available(make_request: _RequestMaker) -> None:
+    req = make_request("GET", "/")
+    ws = web.WebSocketResponse()
+    # Simulate transport being None
+    req._protocol.transport = None
+    with pytest.raises(RuntimeError, match="Transport is not available"):
+        await ws.prepare(req)