Adding additional Wort late in the boil

Brewing Processes
1

Currently doing a 90 minute boil and may have issues with post boil volume being too low.  I have a couple gallons of wort left over from my batch sparge so I was wondering if I could add a gallon or so to my boil at about 45 minutes without messing up too much.  I know since this wort is lower gravity it may screw up th numbers a bit.

Thoughts?

edit:  Just took a refractometer reading of the extra wort and it’s about 10 Brix.

2

Can’t see any major issues with it, the only thing I’d be concerned about is DMS precursors, but at that low gravity and still doing a 45 minute boil on it, I think the impact may be minimal.