diff --git a/definitions/grib1/scanning_mode.def b/definitions/grib1/scanning_mode.def
index ccd4b3c18..ca2c5c60f 100644
--- a/definitions/grib1/scanning_mode.def
+++ b/definitions/grib1/scanning_mode.def
@@ -6,7 +6,9 @@ flagbit iScansNegatively(scanningMode,7)  : dump;
 flagbit jScansPositively(scanningMode,6)  : dump;
 flagbit jPointsAreConsecutive(scanningMode,5)  : dump;
 constant alternativeRowScanning=0 : dump;
+
 transient iScansPositively = !iScansNegatively : constraint;
+transient jScansNegatively = !jScansPositively : constraint;
 
 alias geography.iScansNegatively=iScansNegatively;
 alias geography.jScansPositively=jScansPositively;
diff --git a/definitions/grib2/template.3.scanning_mode.def b/definitions/grib2/template.3.scanning_mode.def
index 6f90222da..793b8946f 100644
--- a/definitions/grib2/template.3.scanning_mode.def
+++ b/definitions/grib2/template.3.scanning_mode.def
@@ -21,6 +21,7 @@ alias geography.jScansPositively=jScansPositively;
 alias geography.jPointsAreConsecutive=jPointsAreConsecutive;
 
 transient iScansPositively = !iScansNegatively : constraint;
+transient jScansNegatively = !jScansPositively : constraint;
 
 flagbit scanningMode5(scanningMode,3) = 0: read_only;
 flagbit scanningMode6(scanningMode,2) = 0: read_only;
diff --git a/tests/grib_change_scanning.sh b/tests/grib_change_scanning.sh
index 9bd8f8561..1f2f5ab29 100755
--- a/tests/grib_change_scanning.sh
+++ b/tests/grib_change_scanning.sh
@@ -121,6 +121,13 @@ status=$?
 set -e
 [ $status -ne 0 ]
 
+# ECC-1492
+grib_check_key_equals "$ECCODES_SAMPLES_PATH/GRIB1.tmpl" iScansNegatively,iScansPositively '0 1'
+grib_check_key_equals "$ECCODES_SAMPLES_PATH/GRIB1.tmpl" jScansNegatively,jScansPositively '1 0'
+
+grib_check_key_equals "$ECCODES_SAMPLES_PATH/GRIB2.tmpl" iScansNegatively,iScansPositively '0 1'
+grib_check_key_equals "$ECCODES_SAMPLES_PATH/GRIB2.tmpl" jScansNegatively,jScansPositively '1 0'
+
 # Clean up
 rm -f $tempFilt $tempGribA $tempGribB $tempRef $tempText
 rm -f ${data_dir}/scan1.grib ${data_dir}/scan.grib