Error when Using nixops deploy to virtual box on macOS High Sierra 10.13.6 (17G65)

Hi, everyone!
I am new to nix and nixops. I was testing deploying a simple setup to virtual box, but failed miserably and I can’t find a fix. I appreciate any help. More info below.

❱ uname -a
Darwin athena.local 17.7.0 Darwin Kernel Version 17.7.0: Thu Jun 21 22:53:14 PDT 2018; root:xnu-4570.71.2~1/RELEASE_X86_64 x86_64 i386 MacBookPro14,3 Darwin

❱ nix-env --version
nix-env (Nix) 2.0.4

❱ nixops --version
NixOps 1.6

❱ ls
trivial-vbox.nix  trivial.nix

❱ cat trivial.nix
{
  network.description = "Web server";

  webserver =
    { config, pkgs, ... }:
    { services.httpd.enable = true;
      services.httpd.adminAddr = "alice@example.org";
      services.httpd.documentRoot = "${pkgs.valgrind.doc}/share/doc/valgrind/html";
      networking.firewall.allowedTCPPorts = [ 80 ];
    };
}

❱ cat trivial-vbox.nix
{
  webserver =
    { config, pkgs, ... }:
    { deployment.targetEnv = "virtualbox";
      deployment.virtualbox.memorySize = 1024; # megabytes
      deployment.virtualbox.vcpu = 2; # number of cpus
    };
}

❱ nixops create ./trivial.nix ./trivial-vbox.nix -d trivial-vbox
created deployment ‘144aa68f-91a5-11e8-861b-acde48001122’
144aa68f-91a5-11e8-861b-acde48001122

❱ nixops deploy -d trivial-vbox --show-trace
error: while evaluating the attribute 'keys' at /nix/store/ajmmfh21zjcma6qwlqxavrx1y0naklx3-nixpkgs-18.09pre146471.d7d31fea7e7/nixpkgs/lib/attrsets.nix:200:46:
while evaluating anonymous function at /nix/store/ajmmfh21zjcma6qwlqxavrx1y0naklx3-nixpkgs-18.09pre146471.d7d31fea7e7/nixpkgs/lib/options.nix:118:41, called from /nix/store/ajmmfh21zjcma6qwlqxavrx1y0naklx3-nixpkgs-18.09pre146471.d7d31fea7e7/nixpkgs/lib/attrsets.nix:200:54:
while evaluating 'scrubOptionValue' at /nix/store/ajmmfh21zjcma6qwlqxavrx1y0naklx3-nixpkgs-18.09pre146471.d7d31fea7e7/nixpkgs/lib/options.nix:114:22, called from /nix/store/ajmmfh21zjcma6qwlqxavrx1y0naklx3-nixpkgs-18.09pre146471.d7d31fea7e7/nixpkgs/lib/options.nix:118:44:
while evaluating 'isDerivation' at /nix/store/ajmmfh21zjcma6qwlqxavrx1y0naklx3-nixpkgs-18.09pre146471.d7d31fea7e7/nixpkgs/lib/attrsets.nix:296:18, called from /nix/store/ajmmfh21zjcma6qwlqxavrx1y0naklx3-nixpkgs-18.09pre146471.d7d31fea7e7/nixpkgs/lib/options.nix:115:8:
while evaluating the attribute 'keys' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/attrsets.nix:200:46:
while evaluating anonymous function at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:75:45, called from /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/attrsets.nix:200:54:
while evaluating the attribute 'value' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:312:9:
while evaluating the option `deployment.keys':
while evaluating the attribute 'isDefined' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:350:5:
while evaluating the attribute 'values' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:338:9:
while evaluating the attribute 'values' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:434:7:
while evaluating anonymous function at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/lists.nix:104:41, called from /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:434:16:
while evaluating anonymous function at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/lists.nix:104:41, called from /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:324:17:
while evaluating anonymous function at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:324:28, called from undefined position:
while evaluating 'dischargeProperties' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:392:25, called from /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:325:62:
while evaluating the attribute 'value' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:216:48:
while evaluating the attribute 'config.keys' at /nix/store/krnkv7vpg24x8rd996av36d85yv4kdp1-nixops-1.6/share/nix/nixops/auto-luks.nix:134:5:
while evaluating the module argument `utils' in "/nix/store/krnkv7vpg24x8rd996av36d85yv4kdp1-nixops-1.6/share/nix/nixops/auto-luks.nix":
while evaluating the attribute '_module.args.utils' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/attrsets.nix:200:46:
while evaluating anonymous function at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:75:45, called from /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/attrsets.nix:200:54:
while evaluating the attribute 'value' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:312:9:
while evaluating the option `_module.args':
while evaluating the attribute 'mergedValue' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:345:5:
while evaluating anonymous function at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:345:32, called from /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:345:19:
while evaluating 'merge' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/types.nix:274:20, called from /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:348:8:
while evaluating anonymous function at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/attrsets.nix:199:9, called from /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/types.nix:275:9:
while evaluating 'filterAttrs' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/attrsets.nix:115:23, called from /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/types.nix:275:35:
while evaluating anonymous function at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/lists.nix:104:41, called from /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/attrsets.nix:116:18:
while evaluating anonymous function at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/attrsets.nix:116:29, called from undefined position:
while evaluating anonymous function at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/types.nix:275:51, called from /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/attrsets.nix:116:62:
while evaluating the attribute 'pkgs_i686' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/attrsets.nix:335:7:
while evaluating anonymous function at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/types.nix:275:86, called from /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/attrsets.nix:335:15:
while evaluating the attribute 'optionalValue' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:352:5:
while evaluating the attribute 'values' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:338:9:
while evaluating the attribute 'values' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:434:7:
while evaluating anonymous function at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/lists.nix:104:41, called from /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:434:16:
while evaluating anonymous function at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/lists.nix:104:41, called from /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:324:17:
while evaluating anonymous function at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:324:28, called from undefined position:
while evaluating 'dischargeProperties' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:392:25, called from /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/modules.nix:325:62:
while evaluating the attribute 'value' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/lib/types.nix:280:55:
while evaluating the attribute 'pkgs_i686' at /nix/var/nix/profiles/per-user/root/channels/nixpkgs/nixos/modules/misc/nixpkgs.nix:207:7:
while evaluating the attribute 'pkgs.pkgsi686Linux' at /nix/store/ajmmfh21zjcma6qwlqxavrx1y0naklx3-nixpkgs-18.09pre146471.d7d31fea7e7/nixpkgs/pkgs/top-level/stage.nix:153:5:
assertion failed at /nix/store/ajmmfh21zjcma6qwlqxavrx1y0naklx3-nixpkgs-18.09pre146471.d7d31fea7e7/nixpkgs/pkgs/top-level/stage.nix:153:21
error: evaluation of the deployment specification failed