diff --git a/files/initrd/opt/arc/include/storage.sh b/files/initrd/opt/arc/include/storage.sh
index 8035a226..00b2a898 100755
--- a/files/initrd/opt/arc/include/storage.sh
+++ b/files/initrd/opt/arc/include/storage.sh
@@ -39,9 +39,9 @@ function getmap() {
       echo -n "${NUMPORTS}" >>"${TMP_PATH}/drivesmax"
       echo -n "${CONPORTS}" >>"${TMP_PATH}/drivescon"
       DISKIDXMAP=$DISKIDXMAP$(printf "%02x" $DISKIDXMAPIDX)
-      let DISKIDXMAPIDX=$DISKIDXMAPIDX+$CONPORTS
+      DISKIDXMAPIDX=$(($DISKIDXMAPIDX + $CONPORTS))
       DISKIDXMAPMAX=$DISKIDXMAPMAX$(printf "%02x" $DISKIDXMAPIDXMAX)
-      let DISKIDXMAPIDXMAX=$DISKIDXMAPIDXMAX+$NUMPORTS
+      DISKIDXMAPIDXMAX=$(($DISKIDXMAPIDXMAX + $NUMPORTS))
       SATADRIVES=$((${SATADRIVES} + ${CONPORTS}))
     done
     # SAS Disks