diff --git a/src/lib/mimeType.js b/src/lib/mimeType.js
index de9a617..0f5c6ad 100644
--- a/src/lib/mimeType.js
+++ b/src/lib/mimeType.js
@@ -46,4 +46,4 @@ export default ext => ({
   "xhtml": "application/xhtml+xml",
   "xml": "application/xml",
   "zip": "application/zip"
-})[ext] ?? 'application/octet-stream';
\ No newline at end of file
+})[ext.toLowerCase()] ?? 'application/octet-stream';
\ No newline at end of file