diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index bdd03cf5d..e5c151046 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -43,3 +43,4 @@ jobs:
 
       - name: Codecov
         uses: codecov/codecov-action@v3
+        if: ${{ matrix.node != 20 }}
diff --git a/test/fn.spec.ts b/test/fn.spec.ts
index a7de2fa53..70b857598 100644
--- a/test/fn.spec.ts
+++ b/test/fn.spec.ts
@@ -3,7 +3,7 @@ import path from 'node:path'
 
 import { jest } from '@jest/globals'
 
-import { _dirname } from './helpers.js'
+import { _dirname, testIf, tsUseEsmSupported } from './helpers.js'
 import type { AsyncWorkerFn } from './types.js'
 
 import { createSyncFn, extractProperties } from 'synckit'
@@ -32,11 +32,13 @@ test('ts as cjs', () => {
   expect(syncFn(5)).toBe(5)
 })
 
-test('ts as esm', () => {
+testIf(tsUseEsmSupported)('ts as esm', () => {
   const syncFn = createSyncFn<AsyncWorkerFn>(workerEsmTsPath)
+  /* eslint-disable jest/no-standalone-expect */
   expect(syncFn(1)).toBe(1)
   expect(syncFn(2)).toBe(2)
   expect(syncFn(5)).toBe(5)
+  /* eslint-enable jest/no-standalone-expect */
 })
 
 test('no ext as js (as esm)', () => {
@@ -46,11 +48,13 @@ test('no ext as js (as esm)', () => {
   expect(syncFn(5)).toBe(5)
 })
 
-test('js as ts (as esm)', () => {
+testIf(tsUseEsmSupported)('js as ts (as esm)', () => {
   const syncFn = createSyncFn<AsyncWorkerFn>(workerJsAsTsPath)
+  /* eslint-disable jest/no-standalone-expect */
   expect(syncFn(1)).toBe(1)
   expect(syncFn(2)).toBe(2)
   expect(syncFn(5)).toBe(5)
+  /* eslint-enable jest/no-standalone-expect */
 })
 
 test('createSyncFn', () => {
diff --git a/test/helpers.ts b/test/helpers.ts
index 2ee292b32..ac197def9 100644
--- a/test/helpers.ts
+++ b/test/helpers.ts
@@ -1,4 +1,15 @@
 import path from 'node:path'
 import { fileURLToPath } from 'node:url'
 
+import { MTS_SUPPORTED_NODE_VERSION } from 'synckit'
+
 export const _dirname = path.dirname(fileURLToPath(import.meta.url))
+
+export const nodeVersion = Number.parseFloat(process.versions.node)
+
+export const tsUseEsmSupported =
+  nodeVersion >= MTS_SUPPORTED_NODE_VERSION &&
+  // ts-jest limitation
+  nodeVersion < 20
+
+export const testIf = (condition: boolean) => (condition ? it : it.skip)
diff --git a/test/ts-runner.spec.ts b/test/ts-runner.spec.ts
index c849ae416..cdb6601a8 100644
--- a/test/ts-runner.spec.ts
+++ b/test/ts-runner.spec.ts
@@ -4,7 +4,7 @@ import path from 'node:path'
 
 import { jest } from '@jest/globals'
 
-import { _dirname } from './helpers.js'
+import { _dirname, nodeVersion, tsUseEsmSupported } from './helpers.js'
 import type { AsyncWorkerFn } from './types.js'
 
 import { MTS_SUPPORTED_NODE_VERSION, TsRunner } from 'synckit'
@@ -34,11 +34,14 @@ test(TsRunner.EsbuildRegister, async () => {
   expect(syncFn(2)).toBe(2)
   expect(syncFn(5)).toBe(5)
 
-  expect(() =>
-    createSyncFn<AsyncWorkerFn>(workerMtsPath, {
-      tsRunner: TsRunner.EsbuildRegister,
-    }),
-  ).toThrow('esbuild-register is not supported for .mts files yet')
+  if (tsUseEsmSupported) {
+    // eslint-disable-next-line jest/no-conditional-expect
+    expect(() =>
+      createSyncFn<AsyncWorkerFn>(workerMtsPath, {
+        tsRunner: TsRunner.EsbuildRegister,
+      }),
+    ).toThrow('esbuild-register is not supported for .mts files yet')
+  }
 })
 
 test(TsRunner.EsbuildRunner, async () => {
@@ -58,11 +61,14 @@ test(TsRunner.EsbuildRunner, async () => {
   expect(syncFn(2)).toBe(2)
   expect(syncFn(5)).toBe(5)
 
-  expect(() =>
-    createSyncFn<AsyncWorkerFn>(workerMtsPath, {
-      tsRunner: TsRunner.EsbuildRunner,
-    }),
-  ).toThrow('esbuild-runner is not supported for .mts files yet')
+  if (tsUseEsmSupported) {
+    // eslint-disable-next-line jest/no-conditional-expect
+    expect(() =>
+      createSyncFn<AsyncWorkerFn>(workerMtsPath, {
+        tsRunner: TsRunner.EsbuildRunner,
+      }),
+    ).toThrow('esbuild-runner is not supported for .mts files yet')
+  }
 })
 
 test(TsRunner.SWC, async () => {
@@ -82,11 +88,14 @@ test(TsRunner.SWC, async () => {
   expect(syncFn(2)).toBe(2)
   expect(syncFn(5)).toBe(5)
 
-  expect(() =>
-    createSyncFn<AsyncWorkerFn>(workerMtsPath, {
-      tsRunner: TsRunner.SWC,
-    }),
-  ).toThrow('swc is not supported for .mts files yet')
+  if (tsUseEsmSupported) {
+    // eslint-disable-next-line jest/no-conditional-expect
+    expect(() =>
+      createSyncFn<AsyncWorkerFn>(workerMtsPath, {
+        tsRunner: TsRunner.SWC,
+      }),
+    ).toThrow('swc is not supported for .mts files yet')
+  }
 })
 
 test(TsRunner.TSX, async () => {
@@ -99,7 +108,7 @@ test(TsRunner.TSX, async () => {
   expect(syncFn(2)).toBe(2)
   expect(syncFn(5)).toBe(5)
 
-  if (Number.parseFloat(process.versions.node) < MTS_SUPPORTED_NODE_VERSION) {
+  if (nodeVersion < MTS_SUPPORTED_NODE_VERSION) {
     // eslint-disable-next-line jest/no-conditional-expect
     expect(() =>
       createSyncFn<AsyncWorkerFn>(workerMtsPath, {
@@ -109,6 +118,10 @@ test(TsRunner.TSX, async () => {
     return
   }
 
+  if (!tsUseEsmSupported) {
+    return
+  }
+
   syncFn = createSyncFn<AsyncWorkerFn>(workerMtsPath, {
     tsRunner: TsRunner.TSX,
   })