diff --git a/builder.sh b/builder.sh
index 9f24bca09917e8d94bd371c5634e834a573a9847..aca8ec1d349af75d81631402eb2c37291384d514 100755
--- a/builder.sh
+++ b/builder.sh
@@ -30,10 +30,10 @@ ARCHITECTURES_DEFAULT=" \
 "
 BRANCH_DEFAULT=experimental
 
-if [ -z ${BRANCH} ]; then
+if [ -z "${BRANCH}" ]; then
 	BRANCH=$BRANCH_DEFAULT
 fi
-if [ -z ${ARCHITECTURES} ]; then
+if [ -z "${ARCHITECTURES}" ]; then
 	ARCHITECTURES=$ARCHITECTURES_DEFAULT
 fi