Why cardano-db-sync does not generate any binary

I use the latest release
git status
HEAD detached at 3.1.0

on build, no binary generated at db-sync-node/bin

studnev@node1-3:~/cardano-db-sync$ nix-build -A cardano-db-sync -o db-sync-node
trace: Using IOHK default nixpkgs
trace: Using index-state: 2020-07-15T00:00:00Z for cardano-db-sync
/nix/store/qa6in63m3i8b69mvdrs3znjbnaz34yp8-cardano-db-sync-exe-cardano-db-sync-3.1.0
studnev@node1-3:~/cardano-db-sync$ ls db-sync-node/
bin/ share/
studnev@node1-3:~/cardano-db-sync$ ls db-sync-node/bin
studnev@node1-3:~/cardano-db-sync$

The issue was resolved by clearing nginx cache manually