diff --git a/lib/make-disk-image.nix b/lib/make-disk-image.nix
index 0180c708..be491f7b 100644
--- a/lib/make-disk-image.nix
+++ b/lib/make-disk-image.nix
@@ -201,7 +201,7 @@ in
         done
         ${installer}
       ''}
-      echo "export origBuilder=$origBuilder" > xchg/saved-env
+      echo "export origBuilder=$origBuilder" >> xchg/saved-env
       ${preVM}
     ''}
     export postVM=${diskoLib.writeCheckedBash { inherit pkgs checked; } "postVM.sh" postVM}