diff --git a/definitions/grib2/stepUnits.def b/definitions/grib2/stepUnits.def
index cffc236be..684aa1f72 100644
--- a/definitions/grib2/stepUnits.def
+++ b/definitions/grib2/stepUnits.def
@@ -4,7 +4,7 @@
 # template_nofail default_step_units "grib2/localConcepts/[centre:s]/default_step_units.def";
 # codetable[1] stepUnits 'stepUnits.table' = defaultStepUnits : transient,dump,no_copy;
 
-meta stepUnits optimal_step_units(forecastTime,indicatorOfUnitOfTimeRange,lengthOfTimeRange,indicatorOfUnitForTimeRange) : transient,dump;
+meta stepUnits optimal_step_units(forecastTime,indicatorOfUnitOfTimeRange,lengthOfTimeRange,indicatorOfUnitForTimeRange) : dump,no_copy;
 transient startStepUnit = 255 : hidden; # 255 means MISSING. See code table 4.4
 transient endStepUnit = 255 : hidden;
 # The lowercase version is to unify it with the helper key in the MARS language