diff --git a/transmit_disfection_protocol.hpp b/transmit_disfection_protocol.hpp
index 53caa3f..3daf37a 100644
--- a/transmit_disfection_protocol.hpp
+++ b/transmit_disfection_protocol.hpp
@@ -254,6 +254,7 @@ typedef struct {
 typedef struct {
   uint32_t total_heap_size;
   uint32_t free_heap_size;
+  uint32_t free_sys_heap_size;
   uint16_t taskNum;
   uint16_t sysHasRun;
 } ack_sysinfo_t;