diff --git a/definitions/grib1/local.98.16.def b/definitions/grib1/local.98.16.def
index f3ff7040a..8ab7c7aad 100644
--- a/definitions/grib1/local.98.16.def
+++ b/definitions/grib1/local.98.16.def
@@ -29,7 +29,7 @@ transient hourOfEndOfOverallTimeInterval=23;
 transient minuteOfEndOfOverallTimeInterval=59;
 transient secondOfEndOfOverallTimeInterval=59;
 
-transient indicatorOfUnitForTimeRange=3;
+transient indicatorOfUnitForTimeRange=3; # month
 transient lengthOfTimeRange=1;
 unsigned[1] averagingPeriod : dump ;