diff --git a/wait_for_pods.sh b/wait_for_pods.sh
index 6d58010..2dedbba 100755
--- a/wait_for_pods.sh
+++ b/wait_for_pods.sh
@@ -28,7 +28,7 @@
 KUBECTL_ARGS=${KUBECTL_ARGS:-}
 
 # use namespace if passed as first arg, or "all" for all namespaces
-if [ ! -z "$1" ]
+if [ -n "$1" ]
 then
   if [[ "$1" == "all" ]]
   then