[clang-format-9] error: unknown key '...'

Clang Frontend Using Clang
#1

Hi cfe-users,

I am using the .clang-format configuration file provided with the latest linux kernel.

https://github.com/torvalds/linux/blob/master/.clang-format

The end of the clang-format file has 3 dots:
…

This is valid YAML Syntax.

However, for some reason, when I run clang-format-9 (Ubuntu 18) I get the following error message:
YAML:504:4: error: unknown key ‘…’
…
^

If I edit the .clang-format file to remove the 3 dots on the final line, clang-format-9 runs successfully and presents the formatted code.

Can someone explain why this error is happening?

Thanks,
Conor