The couple celebrated nine years of marriage on June 25 but the singer was playing a gig in Michigan and was delighted when the crowd surprised him and his wife - who was in the audience - with a special gesture.
He said: "We were playing in upstate Michigan and about three songs in I mentioned it was a special night because Nic was here and it was our anniversary.
"Then all these signs went up, someone had handed them out to everybody, it was like synchronised swimming."