diff --git a/lib/SimpleSAML/Metadata/SAMLParser.php b/lib/SimpleSAML/Metadata/SAMLParser.php
index 8b6f33fe730b521b538fb3ae34b1a1cf1baab2bb..a7fee113ca66925f19aa76afb4813bbdeb5ac1d7 100644
--- a/lib/SimpleSAML/Metadata/SAMLParser.php
+++ b/lib/SimpleSAML/Metadata/SAMLParser.php
@@ -150,7 +150,7 @@ class SimpleSAML_Metadata_SAMLParser
         \SAML2\XML\md\EntityDescriptor $entityElement,
         $maxExpireTime,
         array $validators = array(),
-        array $parentExtensions
+        array $parentExtensions = array()
     ) {
         assert($maxExpireTime === null || is_int($maxExpireTime));