diff --git a/__tests__/index.test.ts b/__tests__/index.test.ts
index 25051afd..ea73174d 100644
--- a/__tests__/index.test.ts
+++ b/__tests__/index.test.ts
@@ -635,7 +635,7 @@ test("nested", async () => {
   const inSource = `${outDir}/this/is/nested/${map.sources[0]}`;
   await expect(fs.pathExists(inSource)).resolves.toBeTruthy();
   const source = await fs.readFile(inSource, "utf8");
-  expect(map.sourcesContent && map.sourcesContent[0]).toBe(source);
+  expect(map.sourcesContent?.[0]).toBe(source);
 });
 
 test("augment-chunk-hash", async () => {
diff --git a/src/index.ts b/src/index.ts
index 2f1a149c..c67d8d4b 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -178,7 +178,10 @@ export default (options: Options = {}): Plugin => {
 
       const getName = (chunk: OutputChunk): string => {
         if (opts.file) return path.basename(opts.file, path.extname(opts.file));
-        if (preserveModules) return path.basename(chunk.fileName, path.extname(chunk.fileName));
+        if (preserveModules) {
+          const { dir, name } = path.parse(chunk.fileName);
+          return dir ? `${dir}/${name}` : name;
+        }
         return chunk.name;
       };