How to prevent Auto-Reboot after flashing Factory Image?

How can I prevent Auto-Reboot of my Nexus 5 after flashing an Official Factory Image?
I've tried to add

Code:

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fastboot reboot-bootloader
ping -n 5 127.0.0.1 >nul

---

after

Code:

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fastboot -w update image-hammerhead-xxxxxx.zip

---

on

flash-all.bat

but the Nexus reboot anyway.
There is another command or option that could help me, or any other way for that?