[Lazarus] SynEdit and gutter behaviour

[Bart]

Hi,

I have a SynEdit on a form and I do this

  SynEdit1.SelText := '//Bye';

This works as expected, and in the gutter the line is now marked as changed.

However if I do this:

  SynEdit1.Lines[1] := SynEdit1.Lines[1] + ' // Hi';

The Line gets updated allright, but the gutter does not mark the line
as changed.

Question:

1: Is this a bug?
2: If it is not a bug, how can I make the gutter mark this line as changed?

Bart