diff --git a/drivers/bluetooth/btmtk.c b/drivers/bluetooth/btmtk.c
index ea7a031000cd..53cba71cb07f 100644
--- a/drivers/bluetooth/btmtk.c
+++ b/drivers/bluetooth/btmtk.c
@@ -188,7 +188,7 @@ int btmtk_setup_firmware_79xx(struct hci_dev *hdev, const char *fwname,
 				       MTK_FW_ROM_PATCH_GD_SIZE +
 				       MTK_FW_ROM_PATCH_SEC_MAP_SIZE * i +
 				       MTK_SEC_MAP_COMMON_SIZE,
-				       MTK_SEC_MAP_NEED_SEND_SIZE + 1);
+				       MTK_SEC_MAP_NEED_SEND_SIZE);
 
 				wmt_params.op = BTMTK_WMT_PATCH_DWNLD;
 				wmt_params.status = &status;