diff --git a/tinyfilemanager.php b/tinyfilemanager.php
index cb326a4..a65d909 100644
--- a/tinyfilemanager.php
+++ b/tinyfilemanager.php
@@ -755,7 +755,7 @@ if (!empty($_FILES) && !FM_READONLY) {
 
     $filename = $f['file']['name'];
     $tmp_name = $f['file']['tmp_name'];
-    $ext = pathinfo($filename, PATHINFO_EXTENSION);
+    $ext = strtolower(pathinfo($filename, PATHINFO_EXTENSION));
     $isFileAllowed = ($allowed) ? in_array($ext, $allowed) : true;
 
     $targetPath = $path . $ds;