Read-only flag not cleared upon Save As

When I open a file read-only (e.g. a file that has mode 444) read-only is in Mousepad's title, Save is disabled. This is expected. Then when I Save the file As another file, the resulting file will be created with correct mode (644), but the read-only flag is not cleared in Mousepad, i.e. the title bar still says read-only and Save is disabled, even though now we are editing a writable file, not the original, read-only file.

Reproduced with Mousepad 0.5.4