Shackell left the Canaries to join Wolves last September, but the central defender struggled to make an impact at Molineux and rejoined City on loan for the rest of the season in February.
Shackell and skipper Doherty have formed a solid partnership at the heart of the Norwich defence, which has helped them move out of the Championship relegation zone.
And Doherty told the club's official website: "I've said it before, the gaffer's done great to get him (Shackell) back. I know his game inside out and there's been no real bedding-in time.
"There have been too many centre-halves at the club, too many combinations and it's been tough at times during the season to get a settled pair with injuries, so that was a big coup for us."