diff --git a/index.mjs b/index.ts
similarity index 95%
rename from index.mjs
rename to index.ts
index 1791d7f..5798937 100644
--- a/index.mjs
+++ b/index.ts
@@ -43,7 +43,7 @@ export function buildConfig ({
 		return finalName;
 	}
 
-	function getOutputFilename (entryPath, ext) {
+	function getOutputFilename (entryPath, ext?) {
 		const base = relative(manifestDirname, dirname(entryPath));
 		return join(base, uniqueFileNameSegment(entryPath, ext));
 	}
@@ -92,8 +92,8 @@ export function buildConfig ({
 							// Emit the asset as part of the build step
 							this.emitFile({
 								type: 'asset',
-								fileName: getOutputFilename(absolutePath),
-								source: readFileSync(absolutePath),
+								fileName: outPath,
+								source: readFileSync(path),
 							});
 						});
 					},