diff --git a/Neos.ContentRepository.Core/Classes/CommandHandlingDependencies.php b/Neos.ContentRepository.Core/Classes/CommandHandlingDependencies.php
index 53a5c282b5c..0763a5dcade 100644
--- a/Neos.ContentRepository.Core/Classes/CommandHandlingDependencies.php
+++ b/Neos.ContentRepository.Core/Classes/CommandHandlingDependencies.php
@@ -65,6 +65,10 @@ public function getContentGraph(WorkspaceName $workspaceName): ContentGraphInter
             return $this->overridenContentGraphInstances[$workspaceName->value];
         }
 
+        if ($workspaceName->isReferencingUnusedContentStream()) {
+            throw new \RuntimeException(sprintf('Expected actual workspace name. Got a workspace name referencing an unused content stream: "%s" instead.', $workspaceName->getReferencingUnusedContentStreamId()->value), 1719648458);
+        }
+
         return $this->contentRepository->getContentGraph($workspaceName);
     }
 
diff --git a/Neos.ContentRepository.Core/Classes/Feature/WorkspaceCommandHandler.php b/Neos.ContentRepository.Core/Classes/Feature/WorkspaceCommandHandler.php
index 1e96149f95f..1a03137b377 100644
--- a/Neos.ContentRepository.Core/Classes/Feature/WorkspaceCommandHandler.php
+++ b/Neos.ContentRepository.Core/Classes/Feature/WorkspaceCommandHandler.php
@@ -900,6 +900,10 @@ private function handleChangeWorkspaceOwner(
 
     private function requireWorkspaceToNotExist(WorkspaceName $workspaceName, CommandHandlingDependencies $commandHandlingDependencies): void
     {
+        if ($workspaceName->isReferencingUnusedContentStream()) {
+            throw new \RuntimeException(sprintf('Expected actual workspace name. Got a workspace name referencing an unused content stream: "%s" instead.', $workspaceName->getReferencingUnusedContentStreamId()->value), 1719648458);
+        }
+
         try {
             $commandHandlingDependencies->getContentGraph($workspaceName);
         } catch (WorkspaceDoesNotExist) {
@@ -918,6 +922,10 @@ private function requireWorkspaceToNotExist(WorkspaceName $workspaceName, Comman
      */
     private function requireWorkspace(WorkspaceName $workspaceName, WorkspaceFinder $workspaceFinder): Workspace
     {
+        if ($workspaceName->isReferencingUnusedContentStream()) {
+            throw new \RuntimeException(sprintf('Expected actual workspace name. Got a workspace name referencing an unused content stream: "%s" instead.', $workspaceName->getReferencingUnusedContentStreamId()->value), 1719648458);
+        }
+
         $workspace = $workspaceFinder->findOneByName($workspaceName);
         if (is_null($workspace)) {
             throw WorkspaceDoesNotExist::butWasSupposedTo($workspaceName);