diff --git a/message_definitions/v1.0/ardupilotmega.xml b/message_definitions/v1.0/ardupilotmega.xml
index b98ad3de1a..165ff8c403 100644
--- a/message_definitions/v1.0/ardupilotmega.xml
+++ b/message_definitions/v1.0/ardupilotmega.xml
@@ -158,8 +158,8 @@
Save without user input (0=require input, 1=autosave).
Delay.
Autoreboot (0=user reboot, 1=autoreboot).
- Empty.
- Empty.
+ Latitude where calibration is happening, for vehicles with no GPS (0 means ignore).
+ Longitude where calibration is happening, for vehicles with no GPS (0 means ignore).
Accept a magnetometer calibration.