diff --git a/build_files/cleanup.sh b/build_files/cleanup.sh
index a5b19bf..e1bb758 100755
--- a/build_files/cleanup.sh
+++ b/build_files/cleanup.sh
@@ -19,7 +19,7 @@ cat /usr/lib/group
 if [ -f /etc/passwd ]; then
   out=$(grep -v "root" /etc/passwd)
 
-  if [ ! -z "$out" ]; then
+  if [[ ! -z "$out" ]]; then
     echo
     echo Appending the following passwd users to /usr/lib/passwd
     echo "$out"
@@ -30,7 +30,7 @@ fi
 if [ -f /etc/group ]; then
   out=$(grep -v "root\|wheel" /etc/group)
 
-  if [ ! -z "$out" ]; then
+  if [[ ! -z "$out" ]]; then
     echo
     echo Appending the following group entries to /usr/lib/group
     echo "$out"