diff --git a/nixos/modules/installer/tools/nixos-generate-config.pl b/nixos/modules/installer/tools/nixos-generate-config.pl
index d3005cdfd6f7..8e75f8d3c40a 100644
--- a/nixos/modules/installer/tools/nixos-generate-config.pl
+++ b/nixos/modules/installer/tools/nixos-generate-config.pl
@@ -474,7 +474,7 @@ my $hwConfig = <<EOF;
   boot.kernelModules = [$kernelModules ];
   boot.extraModulePackages = [$modulePackages ];
 $fsAndSwap
-  nix.maxJobs = $cpus;
+  nix.maxJobs = lib.mkDefault $cpus;
 ${\join "", (map { "  $_\n" } (uniq @attrs))}}
 EOF