diff --git a/src/grib_accessor_class_g2end_step.cc b/src/grib_accessor_class_g2end_step.cc
index b7ae986f3..62b0c9e26 100644
--- a/src/grib_accessor_class_g2end_step.cc
+++ b/src/grib_accessor_class_g2end_step.cc
@@ -546,6 +546,7 @@ static int pack_long_(grib_accessor* a, const long end_step_value, const long en
 
     /*point in time */
     if (self->year == NULL) {
+        err = grib_set_long_internal(h, "startStepUnit", end_step.unit().value<long>());
         err = grib_set_long_internal(h, self->start_step_value, end_step.value<long>());
         return err;
     }
diff --git a/tests/grib_ecc-1620.sh b/tests/grib_ecc-1620.sh
index ecabcb1fd..bcf149ead 100755
--- a/tests/grib_ecc-1620.sh
+++ b/tests/grib_ecc-1620.sh
@@ -41,12 +41,13 @@ grib_check_key_equals()
 }
 
 HOUR=""
-if [ -v ECCODES_GRIB_SHOW_HOUR_STEPUNIT ]; then
+if (set -u; : ${ECCODES_GRIB_SHOW_HOUR_STEPUNIT?}) 2> /dev/null; then
    if [ $ECCODES_GRIB_SHOW_HOUR_STEPUNIT -gt 0 ]; then
       export HOUR="h"
    fi
 fi
 
+
 label="grib_ecc-1620"
 temp=temp.$label
 temp2=temp_2.$label
@@ -56,24 +57,32 @@ instantaneous_field=$data_dir/reduced_gaussian_surface.grib2
 accumulated_field=$data_dir/reduced_gaussian_sub_area.grib2
 
 
-#### Check that step, stepRange, startStep, endStep produce the same result in instantaneous fields
+#### Make sure that step, stepRange, startStep, endStep produce the same result for instantaneous fields
 fn="$instantaneous_field"
 low_level_keys="forecastTime,indicatorOfUnitOfTimeRange:s"
 keys_step="step,step:s,step:i,step:d,stepUnits:s"
 keys_step_range="stepRange,stepRange:s,stepRange:i,stepRange:d,stepUnits:s"
 keys_start_step="startStep,startStep:s,startStep:i,startStep:d,stepUnits:s"
 keys_end_step="endStep,endStep:s,endStep:i,endStep:d,stepUnits:s"
-${tools_dir}/grib_set -s forecastTime=0,indicatorOfUnitOfTimeRange=m $fn $temp
-grib_check_key_equals $temp "-p $low_level_keys" "0 m"
+${tools_dir}/grib_set -s forecastTime=0,indicatorOfUnitOfTimeRange=h $fn $temp
+grib_check_key_equals $temp "-p $low_level_keys" "0 h"
 ${tools_dir}/grib_set -s stepunits=m,step=59 $fn $temp
 grib_check_key_equals $temp "-p $keys_step" "59m 59m 59 59 m"
 grib_check_key_equals $temp "-p $keys_step_range" "59m 59m 59 59 m"
 grib_check_key_equals $temp "-p $keys_start_step" "59m 59m 59 59 m"
 grib_check_key_equals $temp "-p $keys_end_step" "59m 59m 59 59 m"
 
+${tools_dir}/grib_set -s forecastTime=0,indicatorOfUnitOfTimeRange=h $fn $temp
+grib_check_key_equals $temp "-p $low_level_keys" "0 h"
+${tools_dir}/grib_set -s step=59m $fn $temp
+grib_check_key_equals $temp "-p $keys_step" "59m 59m 59 59 m"
+grib_check_key_equals $temp "-p $keys_step_range" "59m 59m 59 59 m"
+grib_check_key_equals $temp "-p $keys_start_step" "59m 59m 59 59 m"
+grib_check_key_equals $temp "-p $keys_end_step" "59m 59m 59 59 m"
 
 
-# if stepUnits is set, then set the low level keys to stepUnits
+#### stepUnits overrides the units in the low level keys
+# if stepUnits=UNIT is set, then set the low level keys to UNIT
 # else optimise low level keys
 # instant fields:
 low_level_keys="forecastTime,indicatorOfUnitOfTimeRange:s,lengthOfTimeRange,indicatorOfUnitForTimeRange:s"