diff --git a/message_definitions/v1.0/ardupilotmega.xml b/message_definitions/v1.0/ardupilotmega.xml
index a55b6bc5dd0..752a569fc3f 100644
--- a/message_definitions/v1.0/ardupilotmega.xml
+++ b/message_definitions/v1.0/ardupilotmega.xml
@@ -1221,6 +1221,9 @@
       <entry value="28" name="COPTER_MODE_TURTLE">
         <description>TURTLE</description>
       </entry>
+      <entry value="29" name="COPTER_MODE_RATE_ACRO">
+        <description>RATE_ACRO</description>
+      </entry>
     </enum>
     <enum name="SUB_MODE">
       <description>A mapping of sub flight modes for custom_mode field of heartbeat.</description>