diff --git a/build.sh b/build.sh
index b6a7a55..067768b 100644
--- a/build.sh
+++ b/build.sh
@@ -3,7 +3,7 @@
 set -e 
 set -x
 
-[ -z "${RPI}" ] ; then
+if [ -z "${RPI}" ] ; do
   echo "${RPI} missing, exting"
   exit 1
 fi