diff --git a/data/grib_data_files.txt b/data/grib_data_files.txt
index f6d3a9124..8996acf97 100644
--- a/data/grib_data_files.txt
+++ b/data/grib_data_files.txt
@@ -91,4 +91,4 @@ mercator.grib2
 run_length_packing.grib2
 boustrophedonic.grib1
 reduced_gaussian_sub_area.legacy.grib1
-
+grid_complex_spatial_differencing.grib2
diff --git a/src/accessor/grib_accessor_class_data_g22order_packing.cc b/src/accessor/grib_accessor_class_data_g22order_packing.cc
index bbc698100..0fefbc6de 100644
--- a/src/accessor/grib_accessor_class_data_g22order_packing.cc
+++ b/src/accessor/grib_accessor_class_data_g22order_packing.cc
@@ -787,7 +787,7 @@ int grib_accessor_class_data_g22order_packing_t::pack_double(grib_accessor* a, c
     // long nvals_per_group     = 0;
     // long nbits_per_group_val = 0;
 
-    long binary_scale_factor, decimal_scale_factor, optimize_scale_factor, typeOfOriginalFieldValues;
+    long binary_scale_factor, decimal_scale_factor, typeOfOriginalFieldValues;
     // long groupSplittingMethodUsed, numberOfGroupsOfDataValues, referenceForGroupWidths;
     long missingValueManagementUsed, primaryMissingValueSubstitute, secondaryMissingValueSubstitute;
     long numberOfBitsUsedForTheGroupWidths, numberOfBitsUsedForTheScaledGroupLengths, orderOfSpatialDifferencing;
@@ -816,7 +816,7 @@ int grib_accessor_class_data_g22order_packing_t::pack_double(grib_accessor* a, c
     if ((err = grib_get_long_internal(gh, self->decimal_scale_factor, &decimal_scale_factor)) != GRIB_SUCCESS)
         return err;
 
-    optimize_scale_factor = 1;  // TODO(masn): To be reviewed
+    int use_scale = 1;
 
     if ((err = grib_get_long_internal(gh, self->binary_scale_factor, &binary_scale_factor)) != GRIB_SUCCESS)
         return err;
@@ -939,7 +939,7 @@ int grib_accessor_class_data_g22order_packing_t::pack_double(grib_accessor* a, c
 
     binary_scale = bin_scale;
 
-    if (optimize_scale_factor == 0) {  // ECMWF style
+    if (use_scale) {  // ECMWF style
         ref       = min_val;
         frange    = max_val - ref;
         dec_scale = 0;
diff --git a/tests/grib_bitmap.sh b/tests/grib_bitmap.sh
index 456f3255e..9ef78550d 100755
--- a/tests/grib_bitmap.sh
+++ b/tests/grib_bitmap.sh
@@ -1,4 +1,4 @@
-#!/bin/sh
+n#!/bin/sh
 # (C) Copyright 2005- ECMWF.
 #
 # This software is licensed under the terms of the Apache Licence Version 2.0
@@ -122,7 +122,9 @@ stats=`${tools_dir}/grib_get -F%.2f -p max,min,avg $tempSimple`
 
 # Repack
 ${tools_dir}/grib_copy -r $infile $temp2
-${tools_dir}/grib_compare -c data:n $infile $temp2
+# The values do not have to be be bit-identical. The high effort to make them bit-identical is not justified.
+# Therefore, we compare the values with a relative tolerance.
+${tools_dir}/grib_compare -R all=0.3 -c data:n $infile $temp2
 grib_check_key_equals $temp2 bitsPerValue 9  # Note: The input file has bpv=9
 
 
@@ -165,5 +167,88 @@ ${tools_dir}/grib_filter $tempRules $data_dir/boustrophedonic.grib1 > $REDIRECT
 ${tools_dir}/grib_filter $tempRules $data_dir/missing_field.grib1 > $REDIRECT
 ${tools_dir}/grib_filter $tempRules $data_dir/reduced_latlon_surface.grib2 > $REDIRECT
 
+# ECC-1858: grid_complex_spatial_differencing
+# Optimize binary_scale_factor, decimal_scale_factor by default
+# ----------------------------------------------------------
+# Repack
+
+in=${data_dir}/grid_complex_spatial_differencing.grib2
+in_with_bitmap=${data_dir}/temp_grid_complex_spatial_differencing_bitmap.grib2
+in_no_bitmap=${data_dir}/temp_grid_complex_spatial_differencing_no_bitmap.grib2
+
+${tools_dir}/grib_set -s bitmapPresent=1 $in $in_with_bitmap 
+${tools_dir}/grib_set -s bitmapPresent=0 $in $in_no_bitmap
+
+# No bitmap
+# Repack
+${tools_dir}/grib_copy -r $in_no_bitmap $temp2
+stats=`${tools_dir}/grib_get -F%.2f -p max,min,avg $temp2`
+[ "$stats" = '549.61 11.61 203.28'  ]
+
+# Rescale
+${tools_dir}/grib_set -s scaleValuesBy=0.001 $in_no_bitmap $temp2
+stats=`${tools_dir}/grib_get -F%.4f -p max,min,avg $temp2`
+[ "$stats" = '0.5496 0.0116 0.2033'  ]
+
+# BitsPerValue=16
+# If required bits and wanted bits are not the same, use an extra bit (see code)
+${tools_dir}/grib_set -s setBitsPerValue=15 $in_no_bitmap $temp2
+stats=`${tools_dir}/grib_get -F%.2f -p max,min,avg $temp2`
+[ "$stats" = '549.61 11.61 203.28'  ]
+grib_check_key_equals $temp2 bitsPerValue 16
+
+# BitsPerValue=24 (see comment above)
+${tools_dir}/grib_set -s setBitsPerValue=23 $in_no_bitmap $temp2
+stats=`${tools_dir}/grib_get -F%.2f -p max,min,avg $temp2`
+[ "$stats" = '549.61 11.61 203.28'  ]
+grib_check_key_equals $temp2 bitsPerValue 24
+
+# Change packing type
+${tools_dir}/grib_set -s packingType=grid_simple $in_no_bitmap $temp2
+stats=`${tools_dir}/grib_get -F%.2f -p max,min,avg $temp2`
+[ "$stats" = '549.61 11.61 203.28'  ]
+
+${tools_dir}/grib_set -s packingType=grid_complex_spatial_differencing $temp2 $tempSimple
+stats=`${tools_dir}/grib_get -F%.2f -p max,min,avg $temp2`
+[ "$stats" = '549.61 11.61 203.28'  ]
+
+# With bitmap
+# Repack
+${tools_dir}/grib_copy -r $in_with_bitmap $temp2
+stats=`${tools_dir}/grib_get -F%.2f -p max,min,avg $temp2`
+[ "$stats" = '549.61 11.61 203.28'  ]
+
+# Rescale
+${tools_dir}/grib_set -s scaleValuesBy=0.001 $in_with_bitmap $temp2
+stats=`${tools_dir}/grib_get -F%.4f -p max,min,avg $temp2`
+[ "$stats" = '0.5496 0.0116 0.2033'  ]
+
+# BitsPerValue=16 (see comment above)
+${tools_dir}/grib_set -s setBitsPerValue=15 $in_with_bitmap $temp2
+stats=`${tools_dir}/grib_get -F%.2f -p max,min,avg $temp2`
+[ "$stats" = '549.61 11.61 203.28'  ]
+grib_check_key_equals $temp2 bitsPerValue 16
+
+# BitsPerValue=24 (see comment above)
+${tools_dir}/grib_set -s setBitsPerValue=23 $in_with_bitmap $temp2
+stats=`${tools_dir}/grib_get -F%.2f -p max,min,avg $temp2`
+[ "$stats" = '549.61 11.61 203.28'  ]
+grib_check_key_equals $temp2 bitsPerValue 24
+
+# Change packing type
+${tools_dir}/grib_set -s packingType=grid_simple $in_with_bitmap $temp2
+stats=`${tools_dir}/grib_get -F%.2f -p max,min,avg $temp2`
+[ "$stats" = '549.61 11.61 203.28'  ]
+
+${tools_dir}/grib_set -s packingType=grid_complex_spatial_differencing $temp2 $tempSimple
+stats=`${tools_dir}/grib_get -F%.2f -p max,min,avg $temp2`
+[ "$stats" = '549.61 11.61 203.28'  ]
+
+# Clean up for ECC-1858
+rm -f $in_with_bitmap $in_no_bitmap
+rm -f $tempSimple
+
+# ----------------------------------------------------------
+
 # Clean up
 rm -f  $tempData1 $tempData2 $temp1 $temp2 $tempRules $tempOut