How to insert text before the first line of an UTF-8 with BOM file

This question is closely related to: https://unix.stackexchange.com/questions/99350/how-to-insert-text-before-the-first-line-of-a-file . I deliberately made the title similar to that question to highlight this. Except the target file is UTF-8 with BOM. So, I want to add a first line to a file that has UTF-8 BOM bytes at its heading (0xef 0xbb 0xbf characters). At least the UTF-8 with BOM files I have here begin with this. If I just go ahead and follow the solutions in the related question, sed "1i My First line is now this." file.txt I will get (in VSCode in my case) something like My First line is now this. ?The first line was this one Second line and so on Being ? in the second line the UTF-8 character to express something non-printable. Another consequence, as one would expect, is the file no longer opens as UTF-8 with BOM and we rely on the text editor features to "guess" its encoding now. We have determined a pattern in our project to have files with BOM to ensure everything is in the same encoding. How do I preserve the BOM header in the file while adding the text?