diff --git a/export-image/prerun.sh b/export-image/prerun.sh
index b95fe36..d9778d1 100755
--- a/export-image/prerun.sh
+++ b/export-image/prerun.sh
@@ -55,7 +55,14 @@ if grep -q "$FEATURE" /etc/mke2fs.conf; then
 	ROOT_FEATURES="^$FEATURE,$ROOT_FEATURES"
 fi
 done
-mkdosfs -n bootfs -F 32 -s 4 -v "$BOOT_DEV" > /dev/null
+
+if [ "$BOOT_SIZE" -lt 134742016 ]; then
+	FAT_SIZE=16
+else
+	FAT_SIZE=32
+fi
+
+mkdosfs -n bootfs -F "$FAT_SIZE" -s 4 -v "$BOOT_DEV" > /dev/null
 mkfs.ext4 -L rootfs -O "$ROOT_FEATURES" "$ROOT_DEV" > /dev/null
 
 mount -v "$ROOT_DEV" "${ROOTFS_DIR}" -t ext4