diff --git a/src/FileAttachmentField.php b/src/FileAttachmentField.php
index ddea293..5725ce8 100644
--- a/src/FileAttachmentField.php
+++ b/src/FileAttachmentField.php
@@ -1298,7 +1298,7 @@ public function getFileClass($filename = null)
         $name = $this->getName();
         $record = $this->getRecord();
 
-        $ext = pathinfo($filename, PATHINFO_EXTENSION);
+        $ext = pathinfo($filename ?? '', PATHINFO_EXTENSION);
         $defaultClass = File::get_class_for_file_extension($ext);
 
         if(empty($name) || empty($record)) {