diff --git a/core/include/thread.h b/core/include/thread.h
index 9c6706672579f29e941ca800d9b9cbe49ca57e5d..3a13e379c853eaf5ed9c020a8d83e28d341003ca 100644
--- a/core/include/thread.h
+++ b/core/include/thread.h
@@ -209,10 +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 };
+#ifdef HAVE_THREAD_ARCH_T
+    thread_arch_t arch;             /**< architecture dependent part    */
+#endif
+};
 
 /**
  * @def THREAD_STACKSIZE_DEFAULT