diff --git a/packages/vitest/src/node/plugins/index.ts b/packages/vitest/src/node/plugins/index.ts
index 4a9e597151a4..fc72f9a3ade9 100644
--- a/packages/vitest/src/node/plugins/index.ts
+++ b/packages/vitest/src/node/plugins/index.ts
@@ -94,6 +94,18 @@ export async function VitestPlugin(
             alias: testConfig.alias,
             conditions: ['node'],
           },
+          // eslint-disable-next-line ts/ban-ts-comment
+          // @ts-ignore Vite 6 compat
+          environments: {
+            ssr: {
+              resolve: {
+                // by default Vite resolves `module` field, which not always a native ESM module
+                // setting this option can bypass that and fallback to cjs version
+                mainFields: [],
+                conditions: ['node'],
+              },
+            },
+          },
           server: {
             ...testConfig.api,
             open,
diff --git a/packages/vitest/src/node/plugins/workspace.ts b/packages/vitest/src/node/plugins/workspace.ts
index bdffdbe16117..491b9200afe5 100644
--- a/packages/vitest/src/node/plugins/workspace.ts
+++ b/packages/vitest/src/node/plugins/workspace.ts
@@ -71,6 +71,18 @@ export function WorkspaceVitestPlugin(
             alias: testConfig.alias,
             conditions: ['node'],
           },
+          // eslint-disable-next-line ts/ban-ts-comment
+          // @ts-ignore Vite 6 compat
+          environments: {
+            ssr: {
+              resolve: {
+                // by default Vite resolves `module` field, which not always a native ESM module
+                // setting this option can bypass that and fallback to cjs version
+                mainFields: [],
+                conditions: ['node'],
+              },
+            },
+          },
           esbuild: viteConfig.esbuild === false
             ? false
             : {
diff --git a/test/core/test/immutable.test.ts b/test/core/test/immutable.test.ts
index 555447c915be..d00e8efa74f6 100644
--- a/test/core/test/immutable.test.ts
+++ b/test/core/test/immutable.test.ts
@@ -1,13 +1,9 @@
-// import im from 'immutable'
-// import { expect, test } from 'vitest'
+import im from 'immutable'
+import { expect, test } from 'vitest'
 
-// test('basic', () => {
-//   expect(im.List([{ x: 1 }])).toEqual(im.List([{ x: 1 }]))
-//   expect(im.List([{ x: 1 }])).toEqual(im.List([1]).map(i => ({ x: i })))
-//   expect(im.List([{ x: 1 }])).not.toEqual(im.List([{ x: 2 }]))
-//   expect(im.List([{ x: 1 }])).not.toEqual(im.List([]))
-// })
-
-import { test } from 'vitest'
-
-test('todo', () => {})
+test('basic', () => {
+  expect(im.List([{ x: 1 }])).toEqual(im.List([{ x: 1 }]))
+  expect(im.List([{ x: 1 }])).toEqual(im.List([1]).map(i => ({ x: i })))
+  expect(im.List([{ x: 1 }])).not.toEqual(im.List([{ x: 2 }]))
+  expect(im.List([{ x: 1 }])).not.toEqual(im.List([]))
+})