diff --git a/main/inc/lib/message.lib.php b/main/inc/lib/message.lib.php
index 291070bf93..0a55fcd9e1 100755
--- a/main/inc/lib/message.lib.php
+++ b/main/inc/lib/message.lib.php
@@ -705,7 +705,11 @@ class MessageManager
         $tbl_message_attach = Database::get_main_table(TABLE_MESSAGE_ATTACHMENT);
 
         // Try to add an extension to the file if it hasn't one
-        $new_file_name = add_ext_on_mime(stripslashes($file_attach['name']), $file_attach['type']);
+        $type = isset($file_attach['type']) ? $file_attach['type'] : '';
+        if (empty($type)) {
+            $type = DocumentManager::file_get_mime_type($file_attach['name']);
+        }
+        $new_file_name = add_ext_on_mime(stripslashes($file_attach['name']), $type);
 
         // user's file name
         $file_name = $file_attach['name'];