diff --git a/pkgs/test/top-level/default.nix b/pkgs/test/top-level/default.nix
index e713b617f8dd..3946b363b764 100644
--- a/pkgs/test/top-level/default.nix
+++ b/pkgs/test/top-level/default.nix
@@ -64,4 +64,22 @@ lib.recurseIntoAttrs {
     assert lib.all (p: p.stdenv.buildPlatform == p.stdenv.hostPlatform) pkgsLocal;
     assert lib.all (p: p.stdenv.buildPlatform != p.stdenv.hostPlatform) pkgsCross;
     pkgs.emptyFile;
+
+  # appendOverlays must preserve splicing so that cross-compilation
+  # works in NixOS modules (which go through appendOverlays via nixpkgs.nix).
+  appendOverlaysPreservesSplicing =
+    let
+      cross = nixpkgsFun {
+        localSystem = {
+          system = "x86_64-linux";
+        };
+        crossSystem = {
+          system = "aarch64-linux";
+        };
+      };
+      appended = cross.appendOverlays [ ];
+    in
+    assert cross.makeWrapper ? __spliced;
+    assert appended.makeWrapper ? __spliced;
+    pkgs.emptyFile;
 }
diff --git a/pkgs/top-level/stage.nix b/pkgs/top-level/stage.nix
index 13bb34e31b39..048ab88854ed 100644
--- a/pkgs/top-level/stage.nix
+++ b/pkgs/top-level/stage.nix
@@ -272,7 +272,10 @@ let
     # in one go when calling Nixpkgs, for performance and simplicity.
     appendOverlays =
       extraOverlays:
-      if extraOverlays == [ ] then self else nixpkgsFun { overlays = args.overlays ++ extraOverlays; };
+      if extraOverlays == [ ] then
+        self.__splicedPackages
+      else
+        nixpkgsFun { overlays = args.overlays ++ extraOverlays; };
 
     # NOTE: each call to extend causes a full nixpkgs rebuild, adding ~130MB
     #       of allocations. DO NOT USE THIS IN NIXPKGS.