diff --git a/lib/SimpleSAML/Configuration.php b/lib/SimpleSAML/Configuration.php
index 71e618ae9492fb7335122bfceddae19716a62503..3440f1e9d7c5e9b9aada272c6757f1ad47fca17f 100644
--- a/lib/SimpleSAML/Configuration.php
+++ b/lib/SimpleSAML/Configuration.php
@@ -118,7 +118,7 @@ class SimpleSAML_Configuration implements \SimpleSAML\Utils\ClearableState
 
             // the file initializes a variable named '$config'
             ob_start();
-            if (interface_exists('Throwable')) {
+            if (interface_exists('Throwable', false)) {
                 try {
                     require($filename);
                 } catch (ParseError $e) {