diff --git a/index.ts b/index.ts
index 638a526..cc3d17d 100644
--- a/index.ts
+++ b/index.ts
@@ -36,7 +36,8 @@ export default {
 			return new Response(`Failed to convert output to UTF-8: ${err}`, { status: 500 })
 		}
 
-		if (query.has('json')) output = JSON.stringify(parseXML(output))
-		return new Response(output)
+		const jsonMode = query.has('json')
+		if (jsonMode) output = JSON.stringify(parseXML(output))
+		return new Response(output, { headers: { 'Content-Type': jsonMode ? 'application/json' : 'text/xml' } })
   }
 }