diff --git a/export-image/prerun.sh b/export-image/prerun.sh
index d9778d1..6a5309a 100755
--- a/export-image/prerun.sh
+++ b/export-image/prerun.sh
@@ -10,7 +10,7 @@ rm -rf "${ROOTFS_DIR}"
 mkdir -p "${ROOTFS_DIR}"
 
 BOOT_SIZE="$((512 * 1024 * 1024))"
-ROOT_SIZE=$(du --apparent-size -s "${EXPORT_ROOTFS_DIR}" --exclude var/cache/apt/archives --exclude boot/firmware --block-size=1 | cut -f 1)
+ROOT_SIZE=$(du -x --apparent-size -s "${EXPORT_ROOTFS_DIR}" --exclude var/cache/apt/archives --exclude boot/firmware --block-size=1 | cut -f 1)
 
 # All partition sizes and starts will be aligned to this size
 ALIGN="$((4 * 1024 * 1024))"