diff --git a/scripts/nix-push.in b/scripts/nix-push.in
index 4a8bdc81b5..9f73b81270 100755
--- a/scripts/nix-push.in
+++ b/scripts/nix-push.in
@@ -104,7 +104,7 @@ close NIX;
 # Build the Nix expression.
 print STDERR "building compressed archives...\n";
 my @narPaths;
-my $pid = open(READ, "$Nix::Config::binDir/nix-build $nixExpr|")
+my $pid = open(READ, "$Nix::Config::binDir/nix-build $nixExpr -o $tmpDir/result |")
     or die "cannot run nix-build";
 while (<READ>) {
     chomp;