diff --git a/src/applications/notification/client/PhabricatorNotificationServerRef.php b/src/applications/notification/client/PhabricatorNotificationServerRef.php
--- a/src/applications/notification/client/PhabricatorNotificationServerRef.php
+++ b/src/applications/notification/client/PhabricatorNotificationServerRef.php
@@ -143,8 +143,10 @@
     return ($this->type == 'admin');
   }
 
-  public function getURI($to_path = null) {
-    $full_path = rtrim($this->getPath(), '/').'/'.ltrim($to_path, '/');
+  public function getURI($to_path = '') {
+    $path = coalesce($this->path, '');
+    $to_path = coalesce($to_path, '');
+    $full_path = rtrim($path, '/').'/'.ltrim($to_path, '/');
 
     $uri = id(new PhutilURI('http://'.$this->getHost()))
       ->setProtocol($this->getProtocol())