diff --git a/bacnet-stack/timesync.c b/bacnet-stack/timesync.c
index 416e27a1..714c420d 100644
--- a/bacnet-stack/timesync.c
+++ b/bacnet-stack/timesync.c
@@ -35,6 +35,7 @@
 #include "bacenum.h"
 #include "bacdcode.h"
 #include "bacdef.h"
+#include "bacapp.h"
 #include "timesync.h"
 
 /* encode service  - use -1 for limit for unlimited */