diff --git a/packages/next/next-server/server/api-utils.ts b/packages/next/next-server/server/api-utils.ts
index f04176eb33d9..07f34d68b66b 100644
--- a/packages/next/next-server/server/api-utils.ts
+++ b/packages/next/next-server/server/api-utils.ts
@@ -229,7 +229,7 @@ export function sendData(
   res: NextApiResponse,
   body: any
 ): void {
-  if (body === null) {
+  if (body === null || body === undefined) {
     res.end()
     return
   }
diff --git a/test/integration/api-support/pages/api/undefined.js b/test/integration/api-support/pages/api/undefined.js
new file mode 100644
index 000000000000..0ccd4fcc75e9
--- /dev/null
+++ b/test/integration/api-support/pages/api/undefined.js
@@ -0,0 +1,3 @@
+export default (req, res) => {
+  res.json(undefined)
+}
diff --git a/test/integration/api-support/test/index.test.js b/test/integration/api-support/test/index.test.js
index a7fec5424ccf..de878765f842 100644
--- a/test/integration/api-support/test/index.test.js
+++ b/test/integration/api-support/test/index.test.js
@@ -122,6 +122,12 @@ function runTests(dev = false) {
     expect(body).toBe(true)
   })
 
+  it('should support undefined response body', async () => {
+    const res = await fetchViaHTTP(appPort, '/api/undefined', null, {})
+    const body = res.ok ? await res.text() : null
+    expect(body).toBe('')
+  })
+
   it('should return error with invalid JSON', async () => {
     const data = await fetchViaHTTP(appPort, '/api/parse', null, {
       method: 'POST',