diff --git a/lib/SimpleSAML/Utils/Config/Metadata.php b/lib/SimpleSAML/Utils/Config/Metadata.php
index 9b586790aba617d0af050d2fab89991a40683695..2bf4b480a41aabadab0f2f5057da807690fe3ac2 100644
--- a/lib/SimpleSAML/Utils/Config/Metadata.php
+++ b/lib/SimpleSAML/Utils/Config/Metadata.php
@@ -117,7 +117,10 @@ class Metadata
 
         // check attributes is an associative array
         if (isset($contact['attributes'])) {
-            if (empty($contact['attributes']) || !is_array($contact['attributes']) || count(array_filter(array_keys($contact['attributes']), 'is_string')) == 0) {
+            if (empty($contact['attributes']) 
+                || !is_array($contact['attributes']) 
+                || count(array_filter(array_keys($contact['attributes']), 'is_string')) === 0
+            ) {
                 throw new \InvalidArgumentException('"attributes" must be an array and cannot be empty.');
             }
         }