diff --git a/.changeset/big-mangos-bow.md b/.changeset/big-mangos-bow.md
new file mode 100644
index 000000000..69a12f884
--- /dev/null
+++ b/.changeset/big-mangos-bow.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Support `lang="postcss"` in addition to `lang="pcss"`
diff --git a/packages/astro/src/core/ssr/css.ts b/packages/astro/src/core/ssr/css.ts
index 83478495a..ab58d6ff4 100644
--- a/packages/astro/src/core/ssr/css.ts
+++ b/packages/astro/src/core/ssr/css.ts
@@ -4,7 +4,7 @@ import path from 'path';
 import { viteifyURL } from '../util.js';
 
 // https://vitejs.dev/guide/features.html#css-pre-processors
-export const STYLE_EXTENSIONS = new Set(['.css', '.pcss', '.scss', '.sass', '.styl', '.stylus', '.less']);
+export const STYLE_EXTENSIONS = new Set(['.css', '.pcss', '.postcss', '.scss', '.sass', '.styl', '.stylus', '.less']);
 
 /** find unloaded styles */
 export function getStylesForURL(filePath: URL, viteServer: vite.ViteDevServer): Set<string> {