diff --git a/include/common/hathreads.h b/include/common/hathreads.h
index 0f10b48..e27ecc6 100644
--- a/include/common/hathreads.h
+++ b/include/common/hathreads.h
@@ -256,6 +256,8 @@
 int  thread_no_sync(void);
 int  thread_need_sync(void);
 
+extern unsigned long all_threads_mask;
+
 #if defined(DEBUG_THREAD) || defined(DEBUG_FULL)
 
 /* WARNING!!! if you update this enum, please also keep lock_label() up to date below */