diff --git a/typo3/sysext/workspaces/Classes/Service/StagesService.php b/typo3/sysext/workspaces/Classes/Service/StagesService.php
index 8c3d2d952728..40b626d8a9fe 100644
--- a/typo3/sysext/workspaces/Classes/Service/StagesService.php
+++ b/typo3/sysext/workspaces/Classes/Service/StagesService.php
@@ -316,7 +316,7 @@ public function getNextStage($stageId)
         $workspaceStageRecs = $this->getStagesForWS();
         if (is_array($workspaceStageRecs) && !empty($workspaceStageRecs)) {
             reset($workspaceStageRecs);
-            while (!is_null($workspaceStageRecKey = key($workspaceStageRecs))) {
+            while ($workspaceStageRecKey = key($workspaceStageRecs) !== null) {
                 $workspaceStageRec = current($workspaceStageRecs);
                 if ($workspaceStageRec['uid'] == $stageId) {
                     $nextStage = next($workspaceStageRecs);
@@ -383,7 +383,7 @@ public function getPrevStage($stageId)
         $workspaceStageRecs = $this->getStagesForWS();
         if (is_array($workspaceStageRecs) && !empty($workspaceStageRecs)) {
             end($workspaceStageRecs);
-            while (!is_null($workspaceStageRecKey = key($workspaceStageRecs))) {
+            while ($workspaceStageRecKey = key($workspaceStageRecs) !== null) {
                 $workspaceStageRec = current($workspaceStageRecs);
                 if ($workspaceStageRec['uid'] == $stageId) {
                     $prevStage = prev($workspaceStageRecs);