Mantis importer creates new project with same name and key

To test whether or not I could import mantis issues in an existing project, I created an empty project with a name and a key.
When I imported a mantis issue list, specifying the exact same project name and key, another project was created with that name and key, instead of putting the issues in the existing project.

The ability to import mantis issues in an existing project is a lack of functionality, but the possibility to create a project with the exact same name and key is a serious bug.