DFU works with BOOT1 floating on nucleo board. Is this an acceptable design?

[Zang Man]

I'm designing a board with STM32F411RE which needs to support DFU for firmware upgrade.

Looking at AN2606 on bootloaders, I will need to use BOOT0 = 1 and BOOT1 = 0 to start in DFU mode.

However, looking at the schematic for the Nucleo f411RE, it looks like they've left BOOT1 (pin28) floating, probably because it doubles up as a GPIO pin after booting.

But when testing DFU on the nucleo and also my prototype circuit, DFU seems to be working fine even though BOOT1 is left floating.

My question is, is this pulled LOW internally and is it okay to leave this floating if I don't intend to use boot from SRAM (which requires BOOT1 = 1)?

[MSipo]

Hope it went well for you. Look at my similar question. I had to connect PB2 to ground (it was floating). https://community.st.com/s/feed/0D53W00001pwlAWSAY