diff --git a/demos/STM32/RT-STM32F746G-DISCOVERY-LWIP-FATFS-USB/cfg/lwipopts.h b/demos/STM32/RT-STM32F746G-DISCOVERY-LWIP-FATFS-USB/cfg/lwipopts.h
index 9ef888687..a91a271aa 100644
--- a/demos/STM32/RT-STM32F746G-DISCOVERY-LWIP-FATFS-USB/cfg/lwipopts.h
+++ b/demos/STM32/RT-STM32F746G-DISCOVERY-LWIP-FATFS-USB/cfg/lwipopts.h
@@ -36,5 +36,7 @@
 #include "static_lwipopts.h"
 
 /* Optional, application-specific settings.*/
+#define TCPIP_MBOX_SIZE                 MEMP_NUM_PBUF
+#define SLIPIF_THREAD_STACKSIZE         1024
 
 #endif /* LWIP_HDR_LWIPOPTS_H__ */