Cannot update from 10.12.6 to 10.13.4

Hello, I'm trying to update my installation but it looks like I cannot select my system drive in the installer. It's greyed out and the texts says "You may not install to this volume because the computer is missing a firmware partition".

How can I fix that? I've tried cloning my system partition to fresh disk but I also couldn't select it in the installer.

submitted by /u/webhdx
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