diff --git a/libraries/AP_Mount/AP_Mount_Siyi.h b/libraries/AP_Mount/AP_Mount_Siyi.h
index c1bddd0699d3f..60e40f4f2c164 100644
--- a/libraries/AP_Mount/AP_Mount_Siyi.h
+++ b/libraries/AP_Mount/AP_Mount_Siyi.h
@@ -27,7 +27,7 @@
 #include <AP_Math/AP_Math.h>
 #include <AP_Common/AP_Common.h>
 
-#define AP_MOUNT_SIYI_PACKETLEN_MAX     22  // maximum number of bytes in a packet sent to or received from the gimbal
+#define AP_MOUNT_SIYI_PACKETLEN_MAX     38  // maximum number of bytes in a packet sent to or received from the gimbal
 
 class AP_Mount_Siyi : public AP_Mount_Backend
 {