diff --git a/tvix/boot/tests/default.nix b/tvix/boot/tests/default.nix
index 5c7f97a1c..a46341c08 100644
--- a/tvix/boot/tests/default.nix
+++ b/tvix/boot/tests/default.nix
@@ -29,12 +29,9 @@ let
       assert isClosure -> importPathName == null;
       assert (!isClosure) -> importPathName != null;
 
-      pkgs.stdenv.mkDerivation {
+      pkgs.stdenv.mkDerivation ({
         name = "run-vm";
 
-        __structuredAttrs = true;
-        exportReferencesGraph.closure = [ path ];
-
         nativeBuildInputs = [
           depot.tvix.store
           depot.tvix.boot.runVM
@@ -76,7 +73,10 @@ let
           grep "${assertVMOutput}" output.txt
         '';
         requiredSystemFeatures = [ "kvm" ];
-      };
+      } // lib.optionalAttrs (isClosure) {
+        __structuredAttrs = true;
+        exportReferencesGraph.closure = [ path ];
+      });
 
   systemFor = sys: (depot.ops.nixos.nixosFor sys).system;