diff --git a/backup.sh b/backup.sh
index 7f7509a..9b2b5fb 100644
--- a/backup.sh
+++ b/backup.sh
@@ -61,14 +61,14 @@ rm ~/$BACKUP_FILENAME
 echo "uploading"
 if [ "$USE_SFTP" -eq 1 ]; then
   cd ~/
-  sshpass -e sftp -oBatchMode=no -b - ${SFTP_USER}@${SFTP_HOST} << !
+  sshpass -e sftp -oBatchMode=no ${SFTP_EXTRA} -b - ${SFTP_USER}@${SFTP_HOST} << !
    cd ${SFTP_PATH}
    put ${BACKUP_FILENAME}.gpg
    bye
 !
   if [ "$month_day" -eq 1 ] ; then
     echo "make monthly backup"
-  sshpass -e sftp -oBatchMode=no -b - ${SFTP_USER}@${SFTP_HOST} << !
+  sshpass -e sftp -oBatchMode=no ${SFTP_EXTRA} -b - ${SFTP_USER}@${SFTP_HOST} << !
    cd ${SFTP_PATH}
    cp ${BACKUP_FILENAME}.gpg ${BACKUP_FILENAME_MONTHLY}.gpg
    bye