diff --git a/tests/data/ref_gfs.landmask.grib1 b/tests/data/ref_gfs.landmask.grib1
new file mode 100644
index 00000000..7053ea1e
Binary files /dev/null and b/tests/data/ref_gfs.landmask.grib1 differ
diff --git a/tests/data/ref_grid_172.landmask.grib1 b/tests/data/ref_grid_172.landmask.grib1
new file mode 100644
index 00000000..001c1a1a
Binary files /dev/null and b/tests/data/ref_grid_172.landmask.grib1 differ
diff --git a/tests/data/ref_grid_220.landmask.grib1 b/tests/data/ref_grid_220.landmask.grib1
new file mode 100644
index 00000000..4f0095ab
Binary files /dev/null and b/tests/data/ref_grid_220.landmask.grib1 differ
diff --git a/tests/run_copygb_tests.sh b/tests/run_copygb_tests.sh
index d749a5c6..664c0555 100755
--- a/tests/run_copygb_tests.sh
+++ b/tests/run_copygb_tests.sh
@@ -7,7 +7,7 @@ set -e
 echo ""
 echo "*** Running copygb test"
 
-# Copy GRIB2 file.
+# Copy GRIB1 file.
 ../src/copygb/copygb -x data/ref_gdaswave.t00z.wcoast.0p16.f000.grib1 test_gdaswave_2.grib1
 
 # Create an index of the copied file.
@@ -17,5 +17,13 @@ echo "*** Running copygb test"
 # so ignore them.
 cmp -i 120 test_gdaswave_2.grib1.idx data/ref_gdaswave_2.grib1.idx
 
+# Interpolate GFS landmask to NCEP grid 172
+../src/copygb/copygb -g172 -x data/ref_gfs.landmask.grib1 172.land.grib1
+cmp 172.land.grib1 data/ref_grid_172.landmask.grib1
+
+# Interpolate GFS landmask to NCEP grid 220
+../src/copygb/copygb -g220 -x data/ref_gfs.landmask.grib1 220.land.grib1
+cmp 220.land.grib1 data/ref_grid_220.landmask.grib1
+
 echo "*** SUCCESS!"
 exit 0