Autocomplete doesn't work for a tag at the start of a line

I’ve noticed that if I start a line with a @ followed by the first few letters of a tag, and then press ESC to generate autocomplete, all I get is the normal word autocomplete, not the list of tags starting with those letters. If I type a space before the @, everything works as it should, but my paragraph alignments are out, and it is a drag having to remember to type the space.
Pretty sure this is a bug?