diff --git a/brewblox_devcon_spark/connection/mqtt_connection.py b/brewblox_devcon_spark/connection/mqtt_connection.py
index 9918af8f..104ff39e 100644
--- a/brewblox_devcon_spark/connection/mqtt_connection.py
+++ b/brewblox_devcon_spark/connection/mqtt_connection.py
@@ -35,14 +35,44 @@ def __init__(self,
         self._handshake_topic = HANDSHAKE_TOPIC + device_id
         self._log_topic = LOG_TOPIC + device_id
 
-    async def _handshake_cb(self, client, topic, payload, qos, properties):
+        self._recv_msg_id: int = 0
+        self._recv_chunks: list[str]
+
+    def _reset_recv_buffer(self, msg_id: int):
+        self._recv_msg_id = msg_id
+        self._recv_chunks = []
+
+    async def _handshake_cb(self, client, topic, payload: bytes, qos, properties):
         if not payload:
             self.disconnected.set()
 
-    async def _resp_cb(self, client, topic, payload, qos, properties):
-        await self.on_response(payload.decode())
-
-    async def _log_cb(self, client, topic, payload, qos, properties):
+    async def _resp_cb(self, client, topic, payload: bytes, qos, properties):
+        try:
+            (msg_id, chunk_idx, chunk) = payload.decode().split(':')
+            msg_id = int(msg_id)
+            chunk_idx = int(chunk_idx)
+        except ValueError as ex:
+            LOGGER.error(f'Failed to parse MQTT payload "{payload}" with error {utils.strex(ex)}')
+            self._reset_recv_buffer(0)
+            return
+
+        if msg_id != self._recv_msg_id:
+            self._reset_recv_buffer(msg_id)
+
+        if len(self._recv_chunks) != chunk_idx:
+            LOGGER.error(f'Received unexpected MQTT message chunk with idx {chunk_idx}')
+            self._reset_recv_buffer(0)
+            return
+
+        self._recv_chunks.append(chunk)
+
+        # we found a message separator - message is done
+        if '\n' in chunk:
+            msg = ''.join(self._recv_chunks).rstrip()
+            self._reset_recv_buffer(0)
+            await self.on_response(msg)
+
+    async def _log_cb(self, client, topic, payload: bytes, qos, properties):
         await self.on_event(payload.decode())
 
     async def send_request(self, msg: str):
diff --git a/firmware.ini b/firmware.ini
index ba46103f..14144bf4 100644
--- a/firmware.ini
+++ b/firmware.ini
@@ -1,7 +1,7 @@
 [FIRMWARE]
-firmware_version=29c23dd7
-firmware_date=2024-05-10
-firmware_sha=29c23dd7f2568cb0e472d8c214ac6b85751e4d7a
+firmware_version=5d1e86a3
+firmware_date=2024-05-13
+firmware_sha=5d1e86a31a3082dcf45eb908470710423d162ef4
 proto_version=06abbc28
 proto_date=2024-05-10
 proto_sha=06abbc281f0919bfb728ca699e916b08b40f0e8f
diff --git a/test/test_connection_mqtt_connection.py b/test/test_connection_mqtt_connection.py
index 7e270af4..be1254e6 100644
--- a/test/test_connection_mqtt_connection.py
+++ b/test/test_connection_mqtt_connection.py
@@ -1,7 +1,7 @@
 import asyncio
 from contextlib import asynccontextmanager
 from datetime import timedelta
-from unittest.mock import AsyncMock
+from unittest.mock import AsyncMock, call
 
 import pytest
 from asgi_lifespan import LifespanManager
@@ -82,9 +82,9 @@ async def on_handshake(client, topic, payload, qos, properties):
         recv_handshake.set()
 
     @mqtt_client.subscribe('brewcast/cbox/req/+')
-    async def on_request(client, topic, payload, qos, properties):
+    async def on_request(client, topic, payload: bytes, qos, properties):
         resp_topic = topic.replace('/req/', '/resp/')
-        mqtt_client.publish(resp_topic, payload[::-1])
+        mqtt_client.publish(resp_topic, f'1:0:{payload.decode()[::-1]}\n'.encode())
         recv_req.set()
 
     @mqtt_client.subscribe('brewcast/cbox/resp/+')
@@ -123,3 +123,20 @@ async def on_log(client, topic, payload, qos, properties):
     # Can safely be called
     await impl.close()
     assert impl.disconnected.is_set()
+
+
+async def test_mqtt_message_handling():
+    callbacks = AsyncMock(spec=connection_handler.ConnectionHandler)
+    impl = mqtt_connection.MqttConnection('1234', callbacks)
+
+    await impl._resp_cb(None, None, '1:0:first,'.encode(), 0, None)
+    await impl._resp_cb(None, None, '2:1:second,'.encode(), 0, None)
+    await impl._resp_cb(None, None, '3:1:third\n'.encode(), 0, None)
+    await impl._resp_cb(None, None, '4:0:fourth\n'.encode(), 0, None)
+    await impl._resp_cb(None, None, '5:0:fifth,'.encode(), 0, None)
+    await impl._resp_cb(None, None, '5:1:fifth-second\n'.encode(), 0, None)
+    await impl._resp_cb(None, None, '6:0:sixth,'.encode(), 0, None)
+    await impl._resp_cb(None, None, 'garbled'.encode(), 0, None)
+    await impl._resp_cb(None, None, '6:1:sixth-second\n'.encode(), 0, None)
+
+    assert callbacks.on_response.await_args_list == [call('fourth'), call('fifth,fifth-second')]