diff --git a/src/asgi/io.rs b/src/asgi/io.rs
index a7068f41..775c22fd 100644
--- a/src/asgi/io.rs
+++ b/src/asgi/io.rs
@@ -218,31 +218,35 @@ impl ASGIHTTPProtocol {
                     more,
                     self.response_chunked.load(atomic::Ordering::Relaxed),
                 ) {
-                    (true, false, false) => {
-                        let (status, headers) = self.response_intent.lock().unwrap().take().unwrap();
-                        self.send_response(
-                            status,
-                            headers,
-                            http_body_util::Full::new(body::Bytes::from(body))
-                                .map_err(std::convert::Into::into)
-                                .boxed(),
-                        );
-                        self.flow_tx_waiter.notify_one();
-                        empty_future_into_py(py)
-                    }
-                    (true, true, false) => {
-                        self.response_chunked.store(true, atomic::Ordering::Relaxed);
-                        let (status, headers) = self.response_intent.lock().unwrap().take().unwrap();
-                        let (body_tx, body_rx) = mpsc::unbounded_channel::<body::Bytes>();
-                        let body_stream = http_body_util::StreamBody::new(
-                            tokio_stream::wrappers::UnboundedReceiverStream::new(body_rx)
-                                .map(body::Frame::data)
-                                .map(Result::Ok),
-                        );
-                        *self.body_tx.lock().unwrap() = Some(body_tx.clone());
-                        self.send_response(status, headers, BodyExt::boxed(body_stream));
-                        self.send_body(py, &body_tx, body, false)
-                    }
+                    (true, false, false) => match self.response_intent.lock().unwrap().take() {
+                        Some((status, headers)) => {
+                            self.send_response(
+                                status,
+                                headers,
+                                http_body_util::Full::new(body::Bytes::from(body))
+                                    .map_err(std::convert::Into::into)
+                                    .boxed(),
+                            );
+                            self.flow_tx_waiter.notify_one();
+                            empty_future_into_py(py)
+                        }
+                        _ => error_flow!("Response already finished"),
+                    },
+                    (true, true, false) => match self.response_intent.lock().unwrap().take() {
+                        Some((status, headers)) => {
+                            self.response_chunked.store(true, atomic::Ordering::Relaxed);
+                            let (body_tx, body_rx) = mpsc::unbounded_channel::<body::Bytes>();
+                            let body_stream = http_body_util::StreamBody::new(
+                                tokio_stream::wrappers::UnboundedReceiverStream::new(body_rx)
+                                    .map(body::Frame::data)
+                                    .map(Result::Ok),
+                            );
+                            *self.body_tx.lock().unwrap() = Some(body_tx.clone());
+                            self.send_response(status, headers, BodyExt::boxed(body_stream));
+                            self.send_body(py, &body_tx, body, false)
+                        }
+                        _ => error_flow!("Response already finished"),
+                    },
                     (true, true, true) => match &*self.body_tx.lock().unwrap() {
                         Some(tx) => self.send_body(py, tx, body, false),
                         _ => error_flow!("Transport not initialized or closed"),
diff --git a/tests/apps/asgi.py b/tests/apps/asgi.py
index a62ab93c..82068bfb 100644
--- a/tests/apps/asgi.py
+++ b/tests/apps/asgi.py
@@ -123,8 +123,26 @@ async def err_app(scope, receive, send):
     1 / 0
 
 
-async def err_proto(scope, receive, send):
-    await send({'type': 'wrong.msg'})
+async def err_proto_msg(scope, receive, send):
+    await send(PLAINTEXT_RESPONSE)
+    try:
+        await send({'type': 'wrong.msg'})
+    except Exception as e:
+        msg = e.args[0]
+    await send({'type': 'http.response.body', 'body': msg.encode('utf8'), 'more_body': False})
+
+
+async def err_proto_flow(scope, receive, send):
+    await send(PLAINTEXT_RESPONSE)
+    await send({'type': 'http.response.body', 'body': b'msg1', 'more_body': False})
+    try:
+        await send({'type': 'http.response.body', 'body': b'msg2', 'more_body': True})
+    except Exception:
+        pass
+    try:
+        await send({'type': 'http.response.body', 'body': b'msg3', 'more_body': False})
+    except Exception:
+        pass
 
 
 async def timeout_n(scope, receive, send):
@@ -172,7 +190,8 @@ def app(scope, receive, send):
         '/ws_echo': ws_echo,
         '/ws_push': ws_push,
         '/err_app': err_app,
-        '/err_proto': err_proto,
+        '/err_proto/type': err_proto_msg,
+        '/err_proto/flow': err_proto_flow,
         '/timeout_n': timeout_n,
         '/timeout_w': timeout_w,
     }.get(scope['path'], info)(scope, receive, send)
diff --git a/tests/test_asgi.py b/tests/test_asgi.py
index f8a76e0d..2489d1d7 100644
--- a/tests/test_asgi.py
+++ b/tests/test_asgi.py
@@ -75,9 +75,13 @@ async def test_app_error(asgi_server, runtime_mode):
 @pytest.mark.parametrize('runtime_mode', ['mt', 'st'])
 async def test_protocol_error(asgi_server, runtime_mode):
     async with asgi_server(runtime_mode, ws=False) as port:
-        res = httpx.get(f'http://localhost:{port}/err_proto')
+        res = httpx.get(f'http://localhost:{port}/err_proto/type')
+        assert res.status_code == 200
+        assert res.text == 'Unsupported ASGI message'
 
-    assert res.status_code == 500
+        res = httpx.get(f'http://localhost:{port}/err_proto/flow')
+        assert res.status_code == 200
+        assert res.text == 'msg1'
 
 
 @pytest.mark.asyncio