Per this documentation page: https://our.umbraco.com/documentation/Extending/Language-Files/ ... buried down the page under the title "User language files" ... it says we should be able to override the default language files by creating our own using the naming syntax: {language}.user.xml.

And, indeed, this used to work quite well under Umbraco 8 and later releases of Umbraco 7.

But when I do this with an Umbraco 9 site I get an error and the site will not run. In my case I created a new file named "en_us.user.xml" that contained the following:

<?xml version="1.0" encoding="utf-8" ?>
<language alias="en_us" intName="English (US)" localName="English (US)" lcid="" culture="en-US">
    <area alias="login">
        <key alias="greeting0">My Test CMS</key>
        <key alias="greeting1">My Test CMS</key>
        <key alias="greeting2">My Test CMS</key>
        <key alias="greeting3">My Test CMS</key>
        <key alias="greeting4">My Test CMS</key>
        <key alias="greeting5">My Test CMS</key>
        <key alias="greeting6">My Test CMS</key>
    </area>
</language>

When I try to load the site I get the following error:

CultureNotFoundException: Culture is not supported. (Parameter 'name') en-us.user is an invalid culture identifier.

Notice it thinks the culture is "en-us.user". Apparently, the filename is being parsed incorrectly.

Anyone else run into this? Find a way around it? Maybe there's a different way to accomplish this than how the documentation describes?