Blank serial number

[digrx]

I'm using Libresdr pluto v0.38 baseclock_cpu750_ddr525.tar.gz
E:\pluto\libiio>iio_info -S
Available contexts:
0: 0456:b673 (Analog Devices Inc. PlutoSDR (ADALM-PLUTO)), serial= [usb:2.29.5]

when using tezuka firmware the serial number appear.
E:\pluto\libiio>iio_info -S
Available contexts:
0: 192.168.2.1 (LibreSDR Rev.5 (Z7020-AD9361)), serial=MZNUHQBLE2NAENEO [ip:libresdr.local]
1: 0456:b673 (Analog Devices Inc. PlutoSDR (ADALM-PLUTO)), serial=MZNUHQBLE2NAENEO [usb:2.30.5]