diff --git a/src/keyboard.c b/src/keyboard.c
index c75e80d2a05..e7b0af9f63c 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -2522,7 +2522,7 @@ read_char (int commandflag, Lisp_Object map,
 	   Lisp_Object prev_event,
 	   bool *used_mouse_menu, struct timespec *end_time)
 {
-  Lisp_Object c;
+  volatile Lisp_Object c;
   sys_jmp_buf local_getcjmp;
   sys_jmp_buf save_jump;
   Lisp_Object tem, save;