diff --git a/lib/plugins/ImportCSS.ts b/lib/plugins/ImportCSS.ts
index 966a317..304359f 100644
--- a/lib/plugins/ImportCSS.ts
+++ b/lib/plugins/ImportCSS.ts
@@ -18,23 +18,43 @@ export const ImportCSSPlugin: () => Plugin = () => {
 	return {
 		name: 'vite-import-css-libmode',
 		enforce: 'post',
-		renderChunk(code, chunk) {
-			if (!chunk.viteMetadata) return
-			const { importedCss } = chunk.viteMetadata
-			if (!importedCss.size) return
+		/**
+		 * Add imports for all splitted CSS assets back to the places where the CSS is used.
+		 *
+		 * We must use `generateBundle` as Vite removes "empty css chunks" (chunks that only import css)
+		 * in its `generateBundle` hook and merged the `importedCss` property down to the really emitted chunks.
+		 * Otherwise we will loose CSS imports!
+		 *
+		 * @param options Output options
+		 * @param bundle The output bundle
+		 */
+		generateBundle(options, bundle) {
+			for (const filename in bundle) {
+				const chunk = bundle[filename]
+				// Make sure chunk is an output chunk with meta data
+				if (!('viteMetadata' in chunk) || !chunk.viteMetadata) {
+					continue
+				}
 
-			/**
-			 * Inject the referenced style files at the top of the chunk.
-			 */
-			const ms = new MagicString(code)
-			for (const cssFileName of importedCss) {
-				let cssFilePath = relative(dirname(chunk.fileName), cssFileName)
-				cssFilePath = cssFilePath.startsWith('.') ? cssFilePath : `./${cssFilePath}`
-				ms.prepend(`import '${cssFilePath}';\n`)
-			}
-			return {
-				code: ms.toString(),
-				map: ms.generateMap(),
+				// Check if the chunk imported CSS, if not we can skip
+				const { importedCss } = chunk.viteMetadata
+				if (!importedCss.size) {
+					continue
+				}
+
+				// Inject the referenced style files at the top of the chunk.
+				const ms = new MagicString(chunk.code)
+				for (const cssFileName of importedCss) {
+					let cssFilePath = relative(dirname(chunk.fileName), cssFileName)
+					cssFilePath = cssFilePath.startsWith('.') ? cssFilePath : `./${cssFilePath}`
+					if (options.format === 'es') {
+						ms.prepend(`import '${cssFilePath}';\n`)
+					} else {
+						ms.prepend(`require('${cssFilePath}');\n`)
+					}
+				}
+				chunk.code = ms.toString()
+				chunk.map = ms.generateMap()
 			}
 		},
 	}