diff --git a/packages/build/src/source/resource/Reader.ts b/packages/build/src/source/resource/Reader.ts
index f79dcc2e..9990fce1 100644
--- a/packages/build/src/source/resource/Reader.ts
+++ b/packages/build/src/source/resource/Reader.ts
@@ -43,7 +43,9 @@ export default class ResourceReader
 
     #makeResourceFilename(filename: string): string
     {
-        const fullFilename = this.#fileHelper.assureExtension(filename);
+        const fullFilename = this.#fileManager.isDirectory(filename)
+            ? `${filename}/index.js`
+            : this.#fileHelper.assureExtension(filename);
 
         if (fullFilename.startsWith('./')) return fullFilename.substring(2);
         if (fullFilename.startsWith('/')) return fullFilename.substring(1);
diff --git a/packages/build/src/source/segment/Reader.ts b/packages/build/src/source/segment/Reader.ts
index 38eb4d57..b10f361e 100644
--- a/packages/build/src/source/segment/Reader.ts
+++ b/packages/build/src/source/segment/Reader.ts
@@ -122,7 +122,9 @@ export default class SegmentReader
 
     #makeModuleFilename(filename: string): string
     {
-        const fullFilename = this.#fileHelper.assureExtension(filename);
+        const fullFilename = this.#fileManager.isDirectory(filename)
+            ? `${filename}/index.js`
+            : this.#fileHelper.assureExtension(filename);
 
         if (fullFilename.startsWith('./')) return fullFilename.substring(2);
         if (fullFilename.startsWith('/')) return fullFilename.substring(1);