Thanks all for the answers!
I honestly polarized SB range too much in my head to any flush draw with a pair/flopped straight with a hearts redraw that I made a stupid call: I say stupid because I believe that at that point it's still a fold and the only other option is a shove all-in (that in any case I don't like at this point, because even if he has a pair with a draw we are still 50% 50% at best).
It doesn't change the line I should have used of course, but just if you are curious about it, that's how the pot ended:
Turn Qs
River 4h
SB shows Qh6c and BTN just shows a 6s and mucks the other.