diff --git a/package.json b/package.json
index 6a8f312..93f2f0a 100644
--- a/package.json
+++ b/package.json
@@ -26,14 +26,15 @@
     "rollup-plugin-json": "^4.0.0",
     "rollup-plugin-node-globals": "^1.4.0",
     "rollup-plugin-node-resolve": "^5.2.0",
+    "rollup-plugin-postcss": "^4.0.1",
     "sinon": "^11.1.1",
-    "subfont": "^6.2.0",
+    "subfont": "^6.3.1",
     "unexpected": "^12.0.0",
     "unexpected-dom": "^5.0.0",
     "unexpected-resemble": "^5.0.0",
     "unexpected-sinon": "^11.0.0",
     "urltools": "^0.4.1",
-    "webpack": "^4.43.0"
+    "webpack": "^5.59.1"
   },
   "files": [
     "dist",
diff --git a/rollup-plugin-postcss.js b/rollup-plugin-postcss.js
deleted file mode 100644
index 5ab5f70..0000000
--- a/rollup-plugin-postcss.js
+++ /dev/null
@@ -1,56 +0,0 @@
-'use strict';
-
-const path = require('path');
-
-const webpack = require('webpack');
-const MemoryFS = require('memory-fs');
-
-const postcss = require.resolve('postcss');
-
-module.exports = () => ({
-  name: 'rollup-plugin-postcss',
-
-  load(id) {
-    if (id !== postcss) {
-      return null;
-    }
-
-    const memfs = new MemoryFS();
-    const compiler = webpack({
-      entry: 'postcss',
-
-      output: {
-        path: __dirname,
-        filename: 'postcss.js',
-        library: 'postcss',
-        libraryTarget: 'commonjs2',
-      },
-    });
-
-    // Write files to memory, not disk
-    compiler.outputFileSystem = memfs;
-
-    return new Promise((resolve, reject) => {
-      compiler.run((err, stats) => {
-        if (err || stats.hasErrors()) {
-          if (err) {
-            return reject(err);
-          }
-
-          const info = stats.toJson();
-
-          return reject(info.errors);
-        }
-
-        return resolve({
-          code: memfs.readFileSync(
-            path.join(__dirname, './postcss.js'),
-            'utf8'
-          ),
-
-          // TODO: figure out source map
-        });
-      });
-    });
-  },
-});
diff --git a/rollup.config.js b/rollup.config.js
index 8045174..8d2dad5 100644
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -8,6 +8,6 @@ module.exports = {
     }),
     require('rollup-plugin-node-globals')(),
     // https://gist.github.com/tivac/d3dd0142e7c52d0d0a5a05b6686340e3
-    require('./rollup-plugin-postcss')(),
+    require('rollup-plugin-postcss')(),
   ],
 };