diff --git a/kernel-src/sys/scheduler/queue.c b/kernel-src/sys/scheduler/queue.c
index 79027c43..51f39c39 100644
--- a/kernel-src/sys/scheduler/queue.c
+++ b/kernel-src/sys/scheduler/queue.c
@@ -227,6 +227,8 @@ found:
 	if (thread->cputarget == NULL)
 		--current_cpu()->stealable_thread_count;
 
+	__assert((thread->flags & THREAD_FLAGS_QUEUED) == 0);
+	__assert((thread->flags & THREAD_FLAGS_RUNNING) == 0);
 	return thread;
 }