Describe the bug

In a test file, I mock a virtual module, e.g. using vi.mock() and try to import the original module using either vi.importActual() or the importOriginal() helper.

vi.mock("virtual:test", async (importOriginal) => {
  const mod = await vi.importActual<"virtual:test">("virtual:test");
  console.log("🚨 mod with vi.importActual:", mod);

  const actual = await importOriginal();
  console.log("🚨 actual with importOriginal:", actual);

  // Not doing anything here for the sake of the repro, just returning the original module.
  return mod;
});

The behavior seems to be different between Vitest 3 and Vitest 4:

Vitest 3: everything seems to work as expected, I can import the original module and get the expected value.
Vitest 4: both vi.importActual() and the importOriginal() helper return what seems to be an empty module (e.g. when logging the result, I get [Object: null prototype] [Module] {})

Reproduction

I've setup a minimal repro available here: https://github.com/HiDeoo/vitest-4-mock-virtual-module-importactual-repro

1. Clone the repository
2. Run pnpm install
3. Run pnpm test

Some tests that are checking the result of calling a function using the virtual module will fail.

A few extra notes:

• Running pnpm add vitest@3 and pnpm test will make the test pass
• I've carefully read the Vitest 4 migration guide, and specifically the section about "Changes to Mocking", but unless I'm missing something, I don't think any of the listed changes explain this behavior.

System Info

System:
    OS: macOS 26.3
    CPU: (8) arm64 Apple M1
    Memory: 96.19 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.14.0 - /Users/hideoo/.local/state/fnm_multishells/42034_1772463011409/bin/node
    npm: 10.9.2 - /Users/hideoo/.local/state/fnm_multishells/42034_1772463011409/bin/npm
    pnpm: 9.15.9 - /Users/hideoo/.local/state/fnm_multishells/42034_1772463011409/bin/pnpm
    bun: 1.3.10 - /opt/homebrew/bin/bun
  Browsers:
    Chrome: 145.0.7632.117
    Firefox: 148.0
    Safari: 26.3
  npmPackages:
    vitest: 4.1.0-beta.5 => 4.1.0-beta.5

Used Package Manager

pnpm

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