diff --git a/zion/object/thread.cpp b/zion/object/thread.cpp
index 701792c..a1a1d47 100644
--- a/zion/object/thread.cpp
+++ b/zion/object/thread.cpp
@@ -120,8 +120,10 @@ void Thread::Cleanup() {
   // 2. Unblock waiting threads.
   while (blocked_threads_.size() != 0) {
     auto thread = blocked_threads_.PopFront();
-    thread->SetState(Thread::RUNNABLE);
-    gScheduler->Enqueue(thread);
+    if (!thread->IsDying()) {
+      thread->SetState(Thread::RUNNABLE);
+      gScheduler->Enqueue(thread);
+    }
   }
 
   // 3. Release Kernel Stack