diff --git a/tests/grib_spectral.sh b/tests/grib_spectral.sh
index c55c9239d..df3bf43f0 100755
--- a/tests/grib_spectral.sh
+++ b/tests/grib_spectral.sh
@@ -12,21 +12,49 @@
 
 label="grib_spectral_test"
 
-output=output.$label.grib
+tempFilt=temp.${label}.filt
+tempGrib=temp.${label}.grib
+
 input_complex=$ECCODES_SAMPLES_PATH/sh_ml_grib2.tmpl
 
-$EXEC ${test_dir}/grib_spectral $input_complex $output
+$EXEC ${test_dir}/grib_spectral $input_complex $tempGrib
 
-rm -f $output
+rm -f $tempGrib
 
 # Now try spectral simple
-input_simple=$label.simple.grib
-${tools_dir}/grib_set  -rs packingType=spectral_simple $input_complex $input_simple
-$EXEC ${test_dir}/grib_spectral $input_simple $output
+tempSimple=temp.$label.simple.grib
+${tools_dir}/grib_set  -rs packingType=spectral_simple $input_complex $tempSimple
+$EXEC ${test_dir}/grib_spectral $tempSimple $tempGrib
 
 # GRIB1: octet_number pack_long
 input_complex=$ECCODES_SAMPLES_PATH/sh_ml_grib1.tmpl
-${tools_dir}/grib_set  -s Nassigned=1 $input_complex $output
+${tools_dir}/grib_set  -s Nassigned=1 $input_complex $tempGrib
 
+# Encode a spectral sample starting from GRIB2.tmpl
+sample2=$ECCODES_SAMPLES_PATH/GRIB2.tmpl
+cat > $tempFilt <<EOF
+    set numberOfDataPoints = 6;
+    set numberOfValues = 6;
+    set bitsPerValue = 16;
+    set values = {33, 0, 1, 0, 2, 0};
+    set typeOfFirstFixedSurface = 105;
+    set scaleFactorOfFirstFixedSurface = 0;
+    set scaledValueOfFirstFixedSurface = 0;
 
-rm -f $output $input_simple
+    set gridDefinitionTemplateNumber=50;
+    set J=1;
+    set K=1;
+    set M=1;
+    set spectralType = 1;
+    set spectralMode = 1;
+
+    set dataRepresentationTemplateNumber=51;
+    write;
+EOF
+${tools_dir}/grib_filter -o $tempGrib $tempFilt $sample2
+${tools_dir}/grib_get_data $tempGrib
+${tools_dir}/grib_dump $tempGrib
+grib_check_key_equals $tempGrib packingType spectral_complex
+grib_check_key_equals $tempGrib gridType sh
+
+rm -f $tempSimple $tempFilt $tempGrib