diff --git a/msg/vehicle_attitude_setpoint.msg b/msg/vehicle_attitude_setpoint.msg
index b3b27874af..da0b01b97f 100644
--- a/msg/vehicle_attitude_setpoint.msg
+++ b/msg/vehicle_attitude_setpoint.msg
@@ -2,9 +2,9 @@ uint64 timestamp		# time since system start (microseconds)
 int8 LANDING_GEAR_UP = 1	# landing gear up
 int8 LANDING_GEAR_DOWN = -1	# landing gear down
 
-float32 roll_body		# body angle in NED frame
-float32 pitch_body		# body angle in NED frame
-float32 yaw_body		# body angle in NED frame
+float32 roll_body		# body angle in NED frame (can be NaN for FW)
+float32 pitch_body		# body angle in NED frame (can be NaN for FW)
+float32 yaw_body		# body angle in NED frame (can be NaN for FW)
 
 float32 yaw_sp_move_rate	# rad/s (commanded by user)