diff --git a/tools/make-dist.sh b/tools/make-dist.sh
index 258d75145daeb0710e0d4f7b23c3522016871f3c..5f42912d559a1e10ac4f7bc5074ca5e153b205d3 100755
--- a/tools/make-dist.sh
+++ b/tools/make-dist.sh
@@ -69,7 +69,7 @@ shift `expr $OPTIND - 1`
 ARCH=
 OS=
 
-if [ -n ${INSTALL_DIR} ]; then
+if [ -n "${INSTALL_DIR}" ]; then
     # Doing direct installation
     if [ $# -lt 1 ]; then
 	usage