Index: src/wp-content/themes/twentytwenty/package.json
===================================================================
--- src/wp-content/themes/twentytwenty/package.json	(revision 50354)
+++ src/wp-content/themes/twentytwenty/package.json	(working copy)
@@ -41,6 +41,11 @@
 		"plugins": [],
 		"map": false
 	},
+	"postcss": {
+		"plugins": {
+			"autoprefixer": {}
+		}
+	},
 	"scripts": {
 		"build": "npm run build:vendor-prefixes && npm run build:rtl",
 		"build:rtl": "concurrently \"npm run build:rtl-style\" \"npm run build:rtl-esb\" \"npm run build:rtl-esc\"",