diff --git a/GD32E50X_BOOT/sys/OTA.cpp b/GD32E50X_BOOT/sys/OTA.cpp
index 080ade4..6d4e879 100644
--- a/GD32E50X_BOOT/sys/OTA.cpp
+++ b/GD32E50X_BOOT/sys/OTA.cpp
@@ -1,4 +1,4 @@
-#include "OTA.h"
+#include "OTA.h"
 #include "Can.h"
 #include "SpiOta.h"
 #include "aes128.h"
@@ -297,10 +297,6 @@ void OTAHandler::process() {
     drainFlashBuffer();
     if (pending_finish_ack && flash_buf_cnt == 0U) {
         pending_finish_ack = false;
-#if DEBUG_PRINT
-        printf("[OTA] flash drain done, send FINISH ACK\r\n");
-#endif
-        send_structured_ack(0xFFFFFFFFU);
     }
 
     if (pending_app_jump) {
@@ -625,7 +621,7 @@ void OTAHandler::handleLinkMessage(ota_link_msg_type_t type, u8 *data, u8 len) {
                 return;
             } else {
                 u32 offset = receive_packet_num * OTA_PACKET_SIZE;
-                if (offset + OTA_PACKET_SIZE > APP_MAX_SIZE) {
+                if (offset >= expected_size) {
                     ota_error = OTA_ERROR_INVALID_SIZE;
                     ota_state = OTA_STATE_IDLE;
                     send_error_frame(receive_packet_num, OTA_ERROR_INVALID_SIZE);
@@ -652,8 +648,7 @@ void OTAHandler::handleLinkMessage(ota_link_msg_type_t type, u8 *data, u8 len) {
             if (receive_IFEND == 0xFFFFFFFFU) {
                 ota_state = OTA_STATE_FINISHED;
                 pending_finish_ack = true;
-                u8 wait_hint[1] = {0x04};
-                send_wait_frame(1, wait_hint);
+                send_structured_ack(0xF0F0F0F0U);
                 return;
             }