Beautifier: FormatAtCursor formats at wrong position

I have bound the action ClangFormat > FormatAtCursor to a keyboard shortcut which I often use to format code while editing.

The problem is when the text beforce the cursor contains umlauts the wrong text is formatted.

int main()
{
	int a1 ;
	int a2 ;
	int a3 ;
	int a4 ;
	// ääääääääääääääääääää
	int a5 ;
	int a6 ;
	int a7 ;
	int a8 ;
	int a9 ;
}

When I position the cursor before a8, the lines containing a6 and a7 are formatted.

The problem is, that ClangFormat::formatAtCursor() forwards the wrong offset to clang-format.
The offset is the character position, but clang-format expect the position in bytes.

Perhaps not directly related, but If I add the character '���' at the beginning of the document it even deletes text, which doesn't happen when I invoke clang-format from the command-line:

// ���
int main()
{
	int a1 ;
	it a2 ;
	it a3 ;
	it a4 ;
	/ ääääääääääääääääääää
	int a5 ;
	it a6 ;
	it a7 ;
	it a8 ;
	int a9 ;
}