diff --git a/src/Core/RuleEngine.php b/src/Core/RuleEngine.php
index d92e121..cf4c0aa 100644
--- a/src/Core/RuleEngine.php
+++ b/src/Core/RuleEngine.php
@@ -24,7 +24,8 @@ class RuleEngine
                 $reflection = new \ReflectionMethod($rule, 'check');
                 $params = $reflection->getParameters();
                 
-                if (isset($params[0]) && $params[0]->getType() && $params[0]->getType()->getName() === 'DOMDocument') {
+                $type = $params[0]->getType();
+                if (isset($params[0]) && $type instanceof \ReflectionNamedType && $type->getName() === 'DOMDocument') {
                     // Document-level rule (Core\AbstractRule style)
                     $violations = $rule->check($doc);
                     $allViolations = array_merge($allViolations, $violations);
diff --git a/src/Rules/HeadingOrderRule.php b/src/Rules/HeadingOrderRule.php
index df079f2..0e7de0d 100644
--- a/src/Rules/HeadingOrderRule.php
+++ b/src/Rules/HeadingOrderRule.php
@@ -16,6 +16,9 @@ class HeadingOrderRule extends AbstractRule
         
         $lastLevel = 0;
         foreach ($headings as $h) {
+            if (!$h instanceof \DOMElement) {
+                continue;
+            }
             $level = (int)substr($h->tagName, 1);
             if ($lastLevel > 0 && $level > $lastLevel + 1) {
                 $violations[] = $this->createViolation(