diff --git a/nuttx-configs/auav-x21/nsh/defconfig b/nuttx-configs/auav-x21/nsh/defconfig
index 3688815ec8..61bea69b49 100644
--- a/nuttx-configs/auav-x21/nsh/defconfig
+++ b/nuttx-configs/auav-x21/nsh/defconfig
@@ -1077,7 +1077,7 @@ CONFIG_CDCACM_NRDREQS=4
 CONFIG_CDCACM_NWRREQS=4
 CONFIG_CDCACM_BULKIN_REQLEN=96
 CONFIG_CDCACM_RXBUFSIZE=600
-CONFIG_CDCACM_TXBUFSIZE=8000
+CONFIG_CDCACM_TXBUFSIZE=2000
 CONFIG_CDCACM_VENDORID=0x26ac
 CONFIG_CDCACM_PRODUCTID=0x0021
 CONFIG_CDCACM_VENDORSTR="AUAV"