diff --git a/lib/eval-config.nix b/lib/eval-config.nix
index 8a7b225e8500..d34a73fd1661 100644
--- a/lib/eval-config.nix
+++ b/lib/eval-config.nix
@@ -11,7 +11,7 @@
 , modules
 }:
 
-let extraArgs_ = extraArgs; pkgs_ = pkgs; in
+let extraArgs_ = extraArgs; pkgs_ = pkgs; system_ = system; in
 
 rec {
 
@@ -39,7 +39,8 @@ rec {
   # Import Nixpkgs, allowing the NixOS option nixpkgs.config to
   # specify the Nixpkgs configuration (e.g., to set package options
   # such as firefox.enableGeckoMediaPlayer, or to apply global
-  # overrides such as changing GCC throughout the system).  This is
+  # overrides such as changing GCC throughout the system), and the
+  # option nixpkgs.system to override the platform type.  This is
   # tricky, because we have to prevent an infinite recursion: "pkgs"
   # is passed as an argument to NixOS modules, but the value of "pkgs"
   # depends on config.nixpkgs.config, which we get from the modules.
@@ -50,12 +51,13 @@ rec {
     then pkgs_
     else import nixpkgs (
       let
+        system = if nixpkgsOptions.system != "" then nixpkgsOptions.system else system_;
         nixpkgsOptions = (import ./eval-config.nix {
           inherit system nixpkgs services extraArgs modules;
           # For efficiency, leave out most NixOS modules; they don't
           # define nixpkgs.config, so it's pointless to evaluate them.
           baseModules = [ ../modules/misc/nixpkgs.nix ];
-          pkgs = import nixpkgs { inherit system; config = {}; };
+          pkgs = import nixpkgs { system = system_; config = {}; };
         }).optionDefinitions.nixpkgs;
       in
       {
diff --git a/modules/misc/nixpkgs.nix b/modules/misc/nixpkgs.nix
index 8173d716d841..d940b32dbd56 100644
--- a/modules/misc/nixpkgs.nix
+++ b/modules/misc/nixpkgs.nix
@@ -13,6 +13,17 @@
       '';
     };
 
+    nixpkgs.system = pkgs.lib.mkOption {
+      default = "";
+      description = ''
+        Specifies the Nix platform type for which NixOS should be built.
+        If unset, it defaults to the platform type of your host system
+        (<literal>${builtins.currentSystem}</literal>).
+        Specifying this option is useful when doing distributed
+        multi-platform deployment, or when building virtual machines.
+      '';
+    };
+
     nixpkgs.platform = pkgs.lib.mkOption {
       default = pkgs.platforms.pc;
       description = ''