diff --git a/lib/xsendfilelib.php b/lib/xsendfilelib.php
index 39106f7..6c78456 100644
--- a/lib/xsendfilelib.php
+++ b/lib/xsendfilelib.php
@@ -52,9 +52,11 @@ function xsendfile($filepath) {
     $aliased = false;
     if (!empty($CFG->xsendfilealiases) and is_array($CFG->xsendfilealiases)) {
         foreach ($CFG->xsendfilealiases as $alias=>$dir) {
-            $dir = realpath($dir).PATH_SEPARATOR;
+            $ds = DIRECTORY_SEPARATOR;
+            $dir = realpath($dir).DIRECTORY_SEPARATOR;
             if (strpos($filepath, $dir) === 0) {
                 $filepath = $alias.substr($filepath, strlen($dir));
+                $filepath = str_replace($ds.$ds, $ds, $filepath);
                 $aliased = true;
                 break;
             }