diff --git a/pkgs/stdenv/generic/default.nix b/pkgs/stdenv/generic/default.nix
index ac727034b8e..be9d38f9780 100644
--- a/pkgs/stdenv/generic/default.nix
+++ b/pkgs/stdenv/generic/default.nix
@@ -127,6 +127,9 @@ let
         "`stdenv.isArm` is deprecated after 18.03. Please use `stdenv.isAarch32` instead"
         hostPlatform.isAarch32;
 
+      # The derivation's `system` is `buildPlatform.system`.
+      inherit (buildPlatform) system;
+
       # Whether we should run paxctl to pax-mark binaries.
       needsPax = isLinux;
 
diff --git a/pkgs/top-level/stage.nix b/pkgs/top-level/stage.nix
index 5ca8b72b8b8..ff09fa5ad1f 100644
--- a/pkgs/top-level/stage.nix
+++ b/pkgs/top-level/stage.nix
@@ -89,7 +89,7 @@ let
     targetPlatform = lib.warn
       "top-level `targetPlatform` is deprecated since 18.09. Please use `stdenv.targetPlatform`."
       super.stdenv.targetPlatform;
-    inherit (super.stdenv.buildPlatform) system;
+    inherit (super.stdenv.hostPlatform) system;
   };
 
   splice = self: super: import ./splice.nix lib self (buildPackages != null);