diff --git a/pkgs/overlays/unstable-from-source.nix b/pkgs/overlays/unstable-from-source.nix
index c7481ff..bca6b9f 100644
--- a/pkgs/overlays/unstable-from-source.nix
+++ b/pkgs/overlays/unstable-from-source.nix
@@ -27,11 +27,13 @@ let
     # crossOverlays -> partial of pkgs.overlays
     # crossOverlays are merged to overlays, not sure what issues that might raise.
     # ignoring.
-  } // (if nixpkgs.stdenv.buildPlatform == nixpkgs.stdenv.hostPlatform then {} else {
+  } // self.lib.optionalAttrs (
+    self.lib.systems.equals nixpkgs.stdenv.buildPlatform nixpkgs.stdenv.hostPlatform
+  ) {
     # workaround for some odd structured packages that changes behaviour
     # when crossSystem is passed.
     crossSystem = sanitizePlatform nixpkgs.stdenv.hostPlatform;
-  });
+  };
 in
 {
   "${attributeName}" = if useUnstable then unstablePkgsForNixpkgs self else self;