diff --git a/README.md b/README.md
index 740b6ca..321acf4 100644
--- a/README.md
+++ b/README.md
@@ -77,7 +77,89 @@ app.register(cookie, {
   - An `Array` can be passed if key rotation is desired. Read more about it in [Rotating signing secret](#rotating-secret).
   - More sophisticated cookie signing mechanisms can be implemented by supplying an `Object`. Read more about it in [Custom cookie signer](#custom-cookie-signer).
 
-- `parseOptions`: An `Object` to pass as options to [cookie parse](https://github.com/jshttp/cookie#cookieparsestr-options).
+- `parseOptions`: An `Object` to modify the serialization of set cookies.
+
+#### parseOptions
+
+##### domain
+
+Specifies the value for the [`Domain` `Set-Cookie` attribute](https://datatracker.ietf.org/doc/html/rfc6265#section-5.2.3). By default, no
+domain is set, and most clients will consider the cookie to apply to only the current domain.
+
+##### encode
+
+Specifies a function that will be used to encode a cookie's value. Since value of a cookie
+has a limited character set (and must be a simple string), this function can be used to encode
+a value into a string suited for a cookie's value.
+
+The default function is the global `encodeURIComponent`, which will encode a JavaScript string
+into UTF-8 byte sequences and then URL-encode any that fall outside of the cookie range.
+
+##### expires
+
+Specifies the `Date` object to be the value for the [`Expires` `Set-Cookie` attribute](https://datatracker.ietf.org/doc/html/rfc6265#section-5.2.1).
+By default, no expiration is set, and most clients will consider this a "non-persistent cookie" and
+will delete it on a condition like exiting a web browser application.
+
+**Note:** the [cookie storage model specification](https://datatracker.ietf.org/doc/html/rfc6265#section-5.3) states that if both `expires` and
+`maxAge` are set, then `maxAge` takes precedence, but it is possible not all clients by obey this,
+so if both are set, they should point to the same date and time.
+
+##### httpOnly
+
+Specifies the `boolean` value for the [`HttpOnly` `Set-Cookie` attribute](https://datatracker.ietf.org/doc/html/rfc6265#section-5.2.6). When truthy,
+the `HttpOnly` attribute is set, otherwise it is not. By default, the `HttpOnly` attribute is not set.
+
+**Note:** be careful when setting this to `true`, as compliant clients will not allow client-side
+JavaScript to see the cookie in `document.cookie`.
+
+##### maxAge
+
+Specifies the `number` (in seconds) to be the value for the [`Max-Age` `Set-Cookie` attribute](https://datatracker.ietf.org/doc/html/rfc6265#section-5.2.2).
+The given number will be converted to an integer by rounding down. By default, no maximum age is set.
+
+**Note:** the [cookie storage model specification](https://datatracker.ietf.org/doc/html/rfc6265#section-5.3) states that if both `expires` and
+`maxAge` are set, then `maxAge` takes precedence, but it is possible not all clients by obey this,
+so if both are set, they should point to the same date and time.
+
+##### partitioned
+
+Specifies the `boolean` value for the [`Partitioned` `Set-Cookie`](https://datatracker.ietf.org/doc/html/draft-cutler-httpbis-partitioned-cookies#section-2.1)
+attribute. When truthy, the `Partitioned` attribute is set, otherwise it is not. By default, the
+`Partitioned` attribute is not set.
+
+⚠️ **Warning:** [This is an attribute that has not yet been fully standardized](https://github.com/fastify/fastify-cookie/pull/261#issuecomment-1803234334), and may change in the future without reflecting the semver versioning. This also means many clients may ignore the attribute until they understand it.
+
+More information about can be found in [the proposal](https://github.com/privacycg/CHIPS).
+
+##### path
+
+Specifies the value for the [`Path` `Set-Cookie` attribute](https://datatracker.ietf.org/doc/html/rfc6265#section-5.2.4). By default, the path
+is considered the ["default path"](https://datatracker.ietf.org/doc/html/rfc6265#section-5.1.4).
+
+##### sameSite
+
+Specifies the `boolean` or `string` to be the value for the [`SameSite` `Set-Cookie` attribute](https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-rfc6265bis-09#section-5.4.7).
+
+  - `true` will set the `SameSite` attribute to `Strict` for strict same site enforcement.
+  - `false` will not set the `SameSite` attribute.
+  - `'lax'` will set the `SameSite` attribute to `Lax` for lax same site enforcement.
+  - `'none'` will set the `SameSite` attribute to `None` for an explicit cross-site cookie.
+  - `'strict'` will set the `SameSite` attribute to `Strict` for strict same site enforcement.
+
+More information about the different enforcement levels can be found in
+[the specification](https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-rfc6265bis-09#section-5.4.7).
+
+**Note:** This is an attribute that has not yet been fully standardized, and may change in the future.
+This also means many clients may ignore this attribute until they understand it.
+
+##### secure
+
+Specifies the `boolean` value for the [`Secure` `Set-Cookie` attribute](https://datatracker.ietf.org/doc/html/rfc6265#section-5.2.5). When truthy,
+the `Secure` attribute is set, otherwise it is not. By default, the `Secure` attribute is not set.
+
+**Note:** be careful when setting this to `true`, as compliant clients will not send the cookie back to
+the server in the future if the browser does not have an HTTPS connection.
 
 ## API
 
diff --git a/cookie.js b/cookie.js
index 349db26..9a8a022 100644
--- a/cookie.js
+++ b/cookie.js
@@ -95,7 +95,7 @@ function parse (str, options) {
     const key = str.substring(pos, eqIdx++).trim()
 
     // only assign once
-    if (undefined === result[key]) {
+    if (result[key] === undefined) {
       const val = (str.charCodeAt(eqIdx) === 0x22)
         ? str.substring(eqIdx + 1, terminatorPos - 1).trim()
         : str.substring(eqIdx, terminatorPos).trim()
@@ -183,6 +183,12 @@ function serialize (name, val, options) {
     str += '; Secure'
   }
 
+  // Draft implementation to support Chrome from 2024-Q1 forward.
+  // See https://datatracker.ietf.org/doc/html/draft-cutler-httpbis-partitioned-cookies#section-2.1
+  if (opt.partitioned) {
+    str += '; Partitioned'
+  }
+
   if (opt.sameSite) {
     const sameSite = typeof opt.sameSite === 'string'
       ? opt.sameSite.toLowerCase()
diff --git a/test/cookie.test.js b/test/cookie.test.js
index 767302a..b05faad 100644
--- a/test/cookie.test.js
+++ b/test/cookie.test.js
@@ -92,6 +92,46 @@ test('should set multiple cookies', (t) => {
   })
 })
 
+test('should set multiple cookies', (t) => {
+  t.plan(12)
+  const fastify = Fastify()
+  fastify.register(plugin)
+
+  fastify.get('/', (req, reply) => {
+    reply
+      .setCookie('foo', 'foo')
+      .cookie('bar', 'test', {
+        partitioned: true
+      })
+      .setCookie('wee', 'woo', {
+        partitioned: true,
+        secure: true
+      })
+      .send({ hello: 'world' })
+  })
+
+  fastify.inject({
+    method: 'GET',
+    url: '/'
+  }, (err, res) => {
+    t.error(err)
+    t.equal(res.statusCode, 200)
+    t.same(JSON.parse(res.body), { hello: 'world' })
+
+    const cookies = res.cookies
+    t.equal(cookies.length, 3)
+    t.equal(cookies[0].name, 'foo')
+    t.equal(cookies[0].value, 'foo')
+    t.equal(cookies[1].name, 'bar')
+    t.equal(cookies[1].value, 'test')
+    t.equal(cookies[2].name, 'wee')
+    t.equal(cookies[2].value, 'woo')
+
+    t.equal(res.headers['set-cookie'][1], 'bar=test; Partitioned')
+    t.equal(res.headers['set-cookie'][2], 'wee=woo; Secure; Partitioned')
+  })
+})
+
 test('cookies get set correctly with millisecond dates', (t) => {
   t.plan(8)
   const fastify = Fastify()
diff --git a/types/plugin.d.ts b/types/plugin.d.ts
index 23e7500..d337675 100644
--- a/types/plugin.d.ts
+++ b/types/plugin.d.ts
@@ -125,9 +125,9 @@ declare namespace fastifyCookie {
     httpOnly?: boolean;
     /**  A `number` in seconds that specifies the `Expires` attribute by adding the specified seconds to the current date. If both `expires` and `maxAge` are set, then `expires` is used. */
     maxAge?: number;
+    partitioned?: boolean;
     /**  The `Path` attribute. Defaults to `/` (the root path).  */
     path?: string;
-    priority?: "low" | "medium" | "high";
     /** A `boolean` or one of the `SameSite` string attributes. E.g.: `lax`, `none` or `strict`.  */
     sameSite?: 'lax' | 'none' | 'strict' | boolean;
     /**  The `boolean` value of the `Secure` attribute. Set this option to false when communicating over an unencrypted (HTTP) connection. Value can be set to `auto`; in this case the `Secure` attribute will be set to false for HTTP request, in case of HTTPS it will be set to true.  Defaults to true. */
diff --git a/types/plugin.test-d.ts b/types/plugin.test-d.ts
index 12ac223..9d8da4d 100644
--- a/types/plugin.test-d.ts
+++ b/types/plugin.test-d.ts
@@ -172,6 +172,7 @@ const parseOptions: fastifyCookieStar.CookieSerializeOptions = {
   sameSite: 'lax',
   secure: true,
   signed: true,
+  partitioned: false,
 };
 expectType<fastifyCookieStar.CookieSerializeOptions>(parseOptions);