diff --git a/.husky/pre-commit b/.husky/pre-commit
index 367adc4..35257ce 100755
--- a/.husky/pre-commit
+++ b/.husky/pre-commit
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/sh -l
 . "$(dirname "$0")/_/husky.sh"
 
 pnpm format && pnpm lint && pnpm build && pnpm test
\ No newline at end of file
diff --git a/src/index.ts b/src/index.ts
index a13e8fe..4511206 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -2,7 +2,7 @@ import { IncomingMessage as Request, ServerResponse as Response } from 'http'
 import { vary } from 'es-vary'
 
 export interface AccessControlOptions {
-  origin?: string | boolean | ((req: Request, res: Response) => string) | Array<string> | RegExp
+  origin?: string | boolean | ((req: Request, res: Response) => string) | Iterable<string> | RegExp
   methods?: string[]
   allowedHeaders?: string[]
   exposedHeaders?: string[]
@@ -12,6 +12,68 @@ export interface AccessControlOptions {
   preflightContinue?: boolean
 }
 
+const isIterable = (obj: unknown): obj is Iterable<unknown> => typeof obj[Symbol.iterator] === 'function'
+
+const failOriginParam = () => {
+  throw new TypeError('No other objects allowed. Allowed types is array of strings or RegExp')
+}
+
+const getOriginHeaderHandler = (origin: unknown): ((req: Request, res: Response) => void) => {
+  if (typeof origin === 'boolean') {
+    return origin
+      ? (_, res) => {
+          res.setHeader('Access-Control-Allow-Origin', '*')
+        }
+      : () => undefined
+  }
+
+  if (typeof origin === 'string') {
+    return (_, res) => {
+      res.setHeader('Access-Control-Allow-Origin', origin)
+    }
+  }
+
+  if (typeof origin === 'function') {
+    return (req, res) => {
+      vary(res, 'Origin')
+      res.setHeader('Access-Control-Allow-Origin', origin(req, res))
+    }
+  }
+
+  if (typeof origin !== 'object') failOriginParam()
+
+  if (isIterable(origin)) {
+    const originArray = Array.from(origin)
+    if (originArray.some((element) => typeof element !== 'string')) failOriginParam()
+
+    const originSet = new Set(origin)
+
+    if (originSet.has('*')) {
+      return (_, res) => {
+        res.setHeader('Access-Control-Allow-Origin', '*')
+      }
+    }
+
+    return (req, res) => {
+      vary(res, 'Origin')
+      if (req.headers.origin === undefined) return
+      if (!originSet.has(req.headers.origin)) return
+      res.setHeader('Access-Control-Allow-Origin', req.headers.origin)
+    }
+  }
+
+  if (origin instanceof RegExp) {
+    return (req, res) => {
+      vary(res, 'Origin')
+      if (req.headers.origin === undefined) return
+      if (!origin.test(req.headers.origin)) return
+      res.setHeader('Access-Control-Allow-Origin', req.headers.origin)
+    }
+  }
+
+  failOriginParam()
+}
+
 /**
  * CORS Middleware
  */
@@ -26,24 +88,10 @@ export const cors = (opts: AccessControlOptions = {}) => {
     optionsSuccessStatus = 204,
     preflightContinue = false
   } = opts
+  const originHeaderHandler = getOriginHeaderHandler(origin)
+
   return (req: Request, res: Response, next?: () => void) => {
-    // Checking the type of the origin property
-    if (typeof origin === 'boolean' && origin === true) {
-      res.setHeader('Access-Control-Allow-Origin', '*')
-    } else if (typeof origin === 'string') {
-      res.setHeader('Access-Control-Allow-Origin', origin)
-    } else if (typeof origin === 'function') {
-      res.setHeader('Access-Control-Allow-Origin', origin(req, res))
-    } else if (typeof origin === 'object') {
-      if (Array.isArray(origin) && (origin.indexOf(req.headers.origin) !== -1 || origin.indexOf('*') !== -1)) {
-        res.setHeader('Access-Control-Allow-Origin', req.headers.origin)
-      } else if (origin instanceof RegExp && origin.test(req.headers.origin)) {
-        res.setHeader('Access-Control-Allow-Origin', req.headers.origin)
-      } else {
-        throw new TypeError('No other objects allowed. Allowed types is array of strings or RegExp')
-      }
-    }
-    if ((typeof origin === 'string' && origin !== '*') || typeof origin === 'function') vary(res, 'Origin')
+    originHeaderHandler(req, res)
 
     // Setting the Access-Control-Allow-Methods header from the methods array
     res.setHeader('Access-Control-Allow-Methods', methods.join(', ').toUpperCase())
diff --git a/tests/index.test.ts b/tests/index.test.ts
index 0a888c1..aa1f671 100644
--- a/tests/index.test.ts
+++ b/tests/index.test.ts
@@ -50,20 +50,44 @@ describe('CORS headers tests', (it) => {
       'http://example.com'
     )
   })
-  it('should set origin if it is an array', async () => {
-    const app = createServer(cors({ origin: ['http://example.com', 'example.com', 'https://example.com'] }))
+  describe('when origin is an array of strings', (it) => {
+    it('should set origin when origin header is included in request and whitelisted', async () => {
+      const app = createServer(cors({ origin: ['http://example.com', 'example.com', 'https://example.com'] }))
 
-    const fetch = makeFetch(app)
+      const fetch = makeFetch(app)
 
-    await fetch('/', { headers: { Origin: 'http://example.com' } }).expect(
-      'Access-Control-Allow-Origin',
-      'http://example.com'
-    )
+      await fetch('/', { headers: { Origin: 'http://example.com' } }).expect(
+        'Access-Control-Allow-Origin',
+        'http://example.com'
+      )
+    })
+    it('should not set origin when origin header is included in request but not whitelisted', async () => {
+      const app = createServer(cors({ origin: ['http://example.com', 'example.com', 'https://example.com'] }))
+
+      const fetch = makeFetch(app)
+
+      await fetch('/', { headers: { Origin: 'http://not-example.com' } }).expect('Access-Control-Allow-Origin', null)
+    })
+    it('should not set origin when origin header is excluded from request', async () => {
+      const app = createServer(cors({ origin: ['http://example.com', 'example.com', 'https://example.com'] }))
+
+      const fetch = makeFetch(app)
+
+      await fetch('/').expect('Access-Control-Allow-Origin', null)
+    })
+  })
+  it('should send an error if origin is an iterable containing a non-string', async () => {
+    try {
+      // @ts-ignore
+      const middleware = cors({ origin: [{}, 3, 'abc'] })
+    } catch (e) {
+      assert.strictEqual(e.message, 'No other objects allowed. Allowed types is array of strings or RegExp')
+    }
   })
   it('should send an error if it is other object types', () => {
     try {
       // @ts-ignore
-      const app = createServer(cors({ origin: { site: 'http://example.com' } }))
+      const middleware = cors({ origin: { site: 'http://example.com' } })
     } catch (e) {
       assert.strictEqual(e.message, 'No other objects allowed. Allowed types is array of strings or RegExp')
     }