diff --git a/xorriso/gen_input.sh b/xorriso/gen_input.sh
index 8af5ca5..a0f3a48 100644
--- a/xorriso/gen_input.sh
+++ b/xorriso/gen_input.sh
@@ -34,7 +34,7 @@ then
     popd > /dev/null
 fi
 
-if [ -f ${PWD}/../sb_pubkey.der ]
+if [ -f "${PWD}/../sb_pubkey.der" ]
 then
 	echo "-map ${PWD}/../sb_pubkey.der sb_pubkey.der"
 	echo "-chmod 0444 /sb_pubkey.der"