diff --git a/libraries/AP_AIS/AP_AIS.cpp b/libraries/AP_AIS/AP_AIS.cpp
index a47c57ee6f..afb141ec53 100644
--- a/libraries/AP_AIS/AP_AIS.cpp
+++ b/libraries/AP_AIS/AP_AIS.cpp
@@ -285,7 +285,7 @@ void AP_AIS::buffer_shift(uint8_t i)
 //////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 // Functions related to the vessel list
 
-// find vessel index in existing list, if not then return new index if possible
+// find vessel index in existing list, if not then return NEW_NOTHROW index if possible
 bool AP_AIS::get_vessel_index(uint32_t mmsi, uint16_t &index, uint32_t lat, uint32_t lon)
 {
     const uint16_t list_size = _list.max_items();
diff --git a/libraries/AP_AIS/AP_AIS.h b/libraries/AP_AIS/AP_AIS.h
index d55a08c82f..2d81c37d1d 100644
--- a/libraries/AP_AIS/AP_AIS.h
+++ b/libraries/AP_AIS/AP_AIS.h
@@ -97,7 +97,7 @@ private:
     // removed the given index from the AIVDM buffer shift following elements
     void buffer_shift(uint8_t i);
 
-    // find vessel in existing list, if not then return new index if possible
+    // find vessel in existing list, if not then return NEW_NOTHROW index if possible
     bool get_vessel_index(uint32_t mmsi, uint16_t &index, uint32_t lat = 0, uint32_t lon = 0) WARN_IF_UNUSED;
     void clear_list_item(uint16_t index);