diff --git a/core/include/thread.h b/core/include/thread.h
index 64a828ab3126caca4fa1feee635b8d43c9377c1e..9c6706672579f29e941ca800d9b9cbe49ca57e5d 100644
--- a/core/include/thread.h
+++ b/core/include/thread.h
@@ -209,7 +209,10 @@ struct _thread {
     const char *name;               /**< thread's name                  */
     int stack_size;                 /**< thread's stack size            */
 #endif
-};
+#ifdef HAVE_THREAD_ARCH_EXT_T 
+    thread_arch_ext_t arch;         /**< architecture dependent exten- 
+                                         sions                          */ 
+#endif };
 
 /**
  * @def THREAD_STACKSIZE_DEFAULT