diff --git a/sim_defs.h b/sim_defs.h
index 5ce87238..2fd85850 100644
--- a/sim_defs.h
+++ b/sim_defs.h
@@ -200,6 +200,7 @@ typedef uint32          t_addr;
 #define SIM_SW_REST     (1u << 27)                      /* attach/restore */
 #define SIM_SW_REG      (1u << 28)                      /* register value */
 #define SIM_SW_STOP     (1u << 29)                      /* stop message */
+#define SIM_SW_SHUT     (1u << 30)                      /* shutdown */
 
 /* Simulator status codes