diff --git a/tools/xen/build_domU.sh b/tools/xen/build_domU.sh
index 7ca6155..8e40225 100755
--- a/tools/xen/build_domU.sh
+++ b/tools/xen/build_domU.sh
@@ -331,13 +331,13 @@
     trap kill_tail SIGINT
 
     echo "Waiting stack.sh to finish..."
-    while ! ssh -q stack@$PUB_IP "grep -q 'stack.sh completed in' run.sh.log" ; do
+    while ! ssh -q stack@$PUB_IP "grep -q 'stack.sh completed in' run.sh.log"; do
         sleep 1
     done
 
     kill $TAIL_PID
 
-    if ! ssh -q stack@$PUB_IP "grep -q 'stack.sh failed' run.sh.log" ; then
+    if ssh -q stack@$PUB_IP "grep -q 'stack.sh failed' run.sh.log"; then
         exit 1
     fi
     echo ""