diff --git a/include/tdep-ia64.h b/include/tdep-ia64.h
index e5751c4c..1fe21293 100644
--- a/include/tdep-ia64.h
+++ b/include/tdep-ia64.h
@@ -164,6 +164,7 @@ struct cursor
 struct ia64_global_unwind_state
   {
     int needs_initialization;
+    pthread_mutex_t lock;		/* global data lock */
 
     /* Table of registers that prologues can save (and order in which
        they're saved).  */