diff --git a/hack/make-rules/test-cmd-util.sh b/hack/make-rules/test-cmd-util.sh
index c38d0aff73b..2e5d3b93efc 100755
--- a/hack/make-rules/test-cmd-util.sh
+++ b/hack/make-rules/test-cmd-util.sh
@@ -5108,7 +5108,7 @@ runTests() {
 
   kube::test::clear_all
 
-  if [ ! -z "${foundError}" ]; then
+  if [[ -n "${foundError}" ]]; then
     echo "FAILED TESTS: ""${foundError}"
     exit 1
   fi