diff --git a/packages/astro/src/core/ssr/rss.ts b/packages/astro/src/core/ssr/rss.ts
index d1f1469b1..93d799f92 100644
--- a/packages/astro/src/core/ssr/rss.ts
+++ b/packages/astro/src/core/ssr/rss.ts
@@ -45,6 +45,7 @@ export function generateRSS(args: GenerateRSSArgs): string {
 		if (!result.link) throw new Error(`[${srcFile}] rss.items required "link" property is missing. got: "${JSON.stringify(result)}"`);
 		xml += `<title><![CDATA[${result.title}]]></title>`;
 		xml += `<link>${canonicalURL(result.link, site).href}</link>`;
+		xml += `<guid>${canonicalURL(result.link, site).href}</guid>`;
 		if (result.description) xml += `<description><![CDATA[${result.description}]]></description>`;
 		if (result.pubDate) {
 			// note: this should be a Date, but if user provided a string or number, we can work with that, too.
diff --git a/packages/astro/test/astro-sitemap-rss.test.js b/packages/astro/test/astro-sitemap-rss.test.js
index a39983196..f193ed77b 100644
--- a/packages/astro/test/astro-sitemap-rss.test.js
+++ b/packages/astro/test/astro-sitemap-rss.test.js
@@ -19,7 +19,7 @@ describe('Sitemaps', () => {
 		it('generates RSS correctly', async () => {
 			const rss = await fixture.readFile('/custom/feed.xml');
 			expect(rss).to.equal(
-				`<?xml version="1.0" encoding="UTF-8"?><rss version="2.0" xmlns:itunes="http://www.itunes.com/dtds/podcast-1.0.dtd" xmlns:content="http://purl.org/rss/1.0/modules/content/"><channel><title><![CDATA[MF Doomcast]]></title><description><![CDATA[The podcast about the things you find on a picnic, or at a picnic table]]></description><link>https://astro.build/custom/feed.xml</link><language>en-us</language><itunes:author>MF Doom</itunes:author><item><title><![CDATA[Rap Snitch Knishes (feat. Mr. Fantastik)]]></title><link>https://astro.build/episode/rap-snitch-knishes/</link><description><![CDATA[Complex named this song the “22nd funniest rap song of all time.”]]></description><pubDate>Tue, 16 Nov 2004 00:00:00 GMT</pubDate><itunes:episodeType>music</itunes:episodeType><itunes:duration>172</itunes:duration><itunes:explicit>true</itunes:explicit></item><item><title><![CDATA[Fazers]]></title><link>https://astro.build/episode/fazers/</link><description><![CDATA[Rhapsody ranked Take Me to Your Leader 17th on its list “Hip-Hop’s Best Albums of the Decade”]]></description><pubDate>Thu, 03 Jul 2003 00:00:00 GMT</pubDate><itunes:episodeType>music</itunes:episodeType><itunes:duration>197</itunes:duration><itunes:explicit>true</itunes:explicit></item><item><title><![CDATA[Rhymes Like Dimes (feat. Cucumber Slice)]]></title><link>https://astro.build/episode/rhymes-like-dimes/</link><description><![CDATA[Operation: Doomsday has been heralded as an underground classic that established MF Doom's rank within the underground hip-hop scene during the early to mid-2000s.
+				`<?xml version="1.0" encoding="UTF-8"?><rss version="2.0" xmlns:itunes="http://www.itunes.com/dtds/podcast-1.0.dtd" xmlns:content="http://purl.org/rss/1.0/modules/content/"><channel><title><![CDATA[MF Doomcast]]></title><description><![CDATA[The podcast about the things you find on a picnic, or at a picnic table]]></description><link>https://astro.build/custom/feed.xml</link><language>en-us</language><itunes:author>MF Doom</itunes:author><item><title><![CDATA[Rap Snitch Knishes (feat. Mr. Fantastik)]]></title><link>https://astro.build/episode/rap-snitch-knishes/</link><guid>https://astro.build/episode/rap-snitch-knishes/</guid><description><![CDATA[Complex named this song the “22nd funniest rap song of all time.”]]></description><pubDate>Tue, 16 Nov 2004 00:00:00 GMT</pubDate><itunes:episodeType>music</itunes:episodeType><itunes:duration>172</itunes:duration><itunes:explicit>true</itunes:explicit></item><item><title><![CDATA[Fazers]]></title><link>https://astro.build/episode/fazers/</link><guid>https://astro.build/episode/fazers/</guid><description><![CDATA[Rhapsody ranked Take Me to Your Leader 17th on its list “Hip-Hop’s Best Albums of the Decade”]]></description><pubDate>Thu, 03 Jul 2003 00:00:00 GMT</pubDate><itunes:episodeType>music</itunes:episodeType><itunes:duration>197</itunes:duration><itunes:explicit>true</itunes:explicit></item><item><title><![CDATA[Rhymes Like Dimes (feat. Cucumber Slice)]]></title><link>https://astro.build/episode/rhymes-like-dimes/</link><guid>https://astro.build/episode/rhymes-like-dimes/</guid><description><![CDATA[Operation: Doomsday has been heralded as an underground classic that established MF Doom's rank within the underground hip-hop scene during the early to mid-2000s.
 ]]></description><pubDate>Tue, 19 Oct 1999 00:00:00 GMT</pubDate><itunes:episodeType>music</itunes:episodeType><itunes:duration>259</itunes:duration><itunes:explicit>true</itunes:explicit></item></channel></rss>`
 			);
 		});