diff --git a/auto/configure b/auto/configure
index a944573a5..e89785fde 100755
--- a/auto/configure
+++ b/auto/configure
@@ -1,3 +1,4 @@
+#!/bin/sh
 
 . auto/options
 . auto/init
diff --git a/src/event/ngx_event_timer.c b/src/event/ngx_event_timer.c
index 8983d997b..79a2e195d 100644
--- a/src/event/ngx_event_timer.c
+++ b/src/event/ngx_event_timer.c
@@ -9,8 +9,8 @@ ngx_mutex_t  *ngx_event_timer_mutex;
 #endif
 
 
-volatile ngx_rbtree_t  *ngx_event_timer_rbtree;
-ngx_rbtree_t            ngx_event_timer_sentinel;
+ngx_thread_volatile ngx_rbtree_t  *ngx_event_timer_rbtree;
+ngx_rbtree_t                       ngx_event_timer_sentinel;
 
 
 ngx_int_t ngx_event_timer_init(ngx_log_t *log)
diff --git a/src/event/ngx_event_timer.h b/src/event/ngx_event_timer.h
index 568a97c0a..21f261f88 100644
--- a/src/event/ngx_event_timer.h
+++ b/src/event/ngx_event_timer.h
@@ -31,8 +31,8 @@ extern ngx_mutex_t  *ngx_event_timer_mutex;
 #endif
 
 
-extern volatile ngx_rbtree_t  *ngx_event_timer_rbtree;
-extern ngx_rbtree_t            ngx_event_timer_sentinel;
+extern ngx_thread_volatile ngx_rbtree_t  *ngx_event_timer_rbtree;
+extern ngx_rbtree_t                       ngx_event_timer_sentinel;
 
 
 ngx_inline static void ngx_event_del_timer(ngx_event_t *ev)
diff --git a/src/os/unix/ngx_thread.h b/src/os/unix/ngx_thread.h
index 8a02880bb..0b065d8ec 100644
--- a/src/os/unix/ngx_thread.h
+++ b/src/os/unix/ngx_thread.h
@@ -7,6 +7,8 @@
 
 #if (NGX_THREADS)
 
+#define ngx_thread_volatile  volatile
+
 #if (NGX_USE_RFORK)
 
 #include <sys/ipc.h>
@@ -96,6 +98,8 @@ extern ngx_int_t ngx_threaded;
 
 #else /* !NGX_THREADS */
 
+#define ngx_thread_volatile
+
 #define ngx_log_tid  0
 #define TID_T_FMT    "%d"