diff --git a/libraries/AP_Rally/AP_Rally.h b/libraries/AP_Rally/AP_Rally.h
index df853824d6..b82ee8c78a 100644
--- a/libraries/AP_Rally/AP_Rally.h
+++ b/libraries/AP_Rally/AP_Rally.h
@@ -27,7 +27,7 @@
 struct PACKED RallyLocation {
     int32_t lat;        //Latitude * 10^7
     int32_t lng;        //Longitude * 10^7
-    int16_t alt;        //transit altitude (and loiter altitude) in meters;
+    int16_t alt;        //transit altitude (and loiter altitude) in meters (absolute);
     int16_t break_alt;  //when autolanding, break out of loiter at this alt (meters)
     uint16_t land_dir;   //when the time comes to auto-land, try to land in this direction (centidegrees)
     uint8_t flags;      //bit 0 = seek favorable winds when choosing a landing poi