diff --git a/nix/nix-daemon/nix-daemon.cc b/nix/nix-daemon/nix-daemon.cc
index 9cfa343d63..e74074f2a3 100644
--- a/nix/nix-daemon/nix-daemon.cc
+++ b/nix/nix-daemon/nix-daemon.cc
@@ -904,6 +904,8 @@ static void daemonLoop()
 
             /* Fork a child to handle the connection. */
             startProcess([&]() {
+                fdSocket.close();
+
                 /* Background the daemon. */
                 if (setsid() == -1)
                     throw SysError(format("creating a new session"));