diff --git a/async_tasks/onboard_tasks.py b/async_tasks/onboard_tasks.py
index c1c684b..42c9b16 100644
--- a/async_tasks/onboard_tasks.py
+++ b/async_tasks/onboard_tasks.py
@@ -42,7 +42,7 @@ async def measure_sensors(
         # Package into message
         for i in range(len(sensors)):
             message = json.dumps({
-                "micro": microcontroller_id,
+                "micro": str(microcontroller_id),
                 "sensor": sensors[i].name,
                 "temperature": temperatures[i],
                 "time": timestamps[i],