diff --git a/tests/grib_lam_bf.c b/tests/grib_lam_bf.c
index 81b9ec137..c07ecc393 100644
--- a/tests/grib_lam_bf.c
+++ b/tests/grib_lam_bf.c
@@ -768,7 +768,16 @@ int main(int argc, char* argv[])
             GRIB_CHECK(grib_set_long(h, "biFourierResolutionSubSetParameterM", trunc[itrunc].subnmsmax), 0);
             GRIB_CHECK(grib_set_long(h, "biFourierSubTruncationType", trunc[itrunc].subtrunc), 0);
             GRIB_CHECK(grib_set_long(h, "biFourierPackingModeForAxes", 1), 0);
-            GRIB_CHECK(grib_set_long(h, "unpackedSubsetPrecision", 2), 0);
+            /* "unpackedSubsetPrecision" value is used for "ieee_floats".
+               ieee_floats=2 means bytes=8 and grib_long_to_ieee64 is used, which is supported
+               only when sizeof(double) == sizeof(long)
+            */
+            long unpackedSubsetPrecision;
+            if (sizeof(double) == sizeof(long))
+                  unpackedSubsetPrecision = 2;
+            else
+                  unpackedSubsetPrecision = 1;
+            GRIB_CHECK(grib_set_long(h, "unpackedSubsetPrecision", unpackedSubsetPrecision), 0);
 
             len = trunc[itrunc].len;
             GRIB_CHECK(grib_set_double_array(h, "values", trunc[itrunc].values, len), 0);