diff --git a/default.nix b/default.nix
index 0cb74ee73..c4db2fa58 100644
--- a/default.nix
+++ b/default.nix
@@ -6,6 +6,7 @@
 , parentTargetMap ? null
 , nixpkgsConfig ? { }
 , localSystem ? builtins.currentSystem
+, crossSystem ? null
 , ...
 }@args:
 
@@ -78,7 +79,7 @@ let
 
 in
 readTree.fix (self: (readDepot {
-  inherit localSystem;
+  inherit localSystem crossSystem;
   depot = self;
 
   # Pass third_party as 'pkgs' (for compatibility with external
diff --git a/third_party/nixpkgs/default.nix b/third_party/nixpkgs/default.nix
index 3fc2aaf7a..84bd500cb 100644
--- a/third_party/nixpkgs/default.nix
+++ b/third_party/nixpkgs/default.nix
@@ -12,6 +12,7 @@
 , externalArgs ? { }
 , depotOverlays ? true
 , localSystem ? externalArgs.localSystem or builtins.currentSystem
+, crossSystem ? externalArgs.crossSystem or localSystem
 , ...
 }:
 
@@ -31,7 +32,7 @@ let
         checkMeta = false;
       };
 
-    inherit localSystem;
+    inherit localSystem crossSystem;
   };
 
   # import the nixos-unstable package set, or optionally use the