diff --git a/library/Icinga/User.php b/library/Icinga/User.php
index 862d6c9de..e3046fb59 100644
--- a/library/Icinga/User.php
+++ b/library/Icinga/User.php
@@ -379,7 +379,11 @@ class User
      */
     public function setDomain($domain)
     {
-        $this->domain = $domain;
+        $domain = trim($domain);
+
+        if (strlen($domain)) {
+            $this->domain = $domain;
+        }
 
         return $this;
     }