diff --git a/lib/SimpleSAML/IdP.php b/lib/SimpleSAML/IdP.php
index c69e29d58ce7c2f333d807d463364504a311b048..ca03d58e2552e00890081ef2aa472d448765abbf 100644
--- a/lib/SimpleSAML/IdP.php
+++ b/lib/SimpleSAML/IdP.php
@@ -537,6 +537,7 @@ class SimpleSAML_IdP {
 				SimpleSAML_Auth_Default::initLogoutReturn($returnTo);
 			} elseif ($authority === 'saml2') {
 				/* SAML 2 SP which isn't an authentication source. */
+				$config = SimpleSAML_Configuration::getInstance();
 				SimpleSAML_Utilities::redirect('/' . $config->getBaseURL() . 'saml2/sp/initSLO.php',
 					array('RelayState' => $returnTo)
 				);