diff --git a/www/saml2/sp/initSSO.php b/www/saml2/sp/initSSO.php
index fecc8f4f4244fb94c8cff8017ea4ca687359e522..1dad4aa0ecfe34141088bdf07a081f36201cc08a 100644
--- a/www/saml2/sp/initSSO.php
+++ b/www/saml2/sp/initSSO.php
@@ -99,7 +99,7 @@ try {
 	$ar->setRelayState($_REQUEST['RelayState']);
 
 	if (isset($_GET['IsPassive'])) {
-		$ar->setIsPassive($_GET['IsPassive']);
+		$ar->setIsPassive((bool)$_GET['IsPassive']);
 	}
 
 	/* Save request information. */