Partial Bootstrap does not work with UTF-8 files (XmlParseException)

We are trying to (partial) bootstrap a file that is UTF-8 and has umlauts inside, e. g. title of a page.

When bootstrapping the file with BootstrapSingleModuleResource task everything is fine. Bootstrapping a complete subtree file with this task also works fine.

When trying to use PartialBootstrapTask with complete website export xml Mgnl crashes with XmlParseException (Invalid byte 2 of 3-byte UTF-8 sequence).

To reproduce:

-create a subpage in a website tree and set title or description to "Grüße"
-export complete tree and save xml as utf-8 file
-create PartialBootstrap task with the node of the subpage