diff --git a/includes/CommentUtils.php b/includes/CommentUtils.php
index d22d53d20..f49457581 100644
--- a/includes/CommentUtils.php
+++ b/includes/CommentUtils.php
@@ -327,17 +327,17 @@ class CommentUtils {
 	 * The indent level is the number of lists inside of which it is nested.
 	 *
 	 * @param Node $node
-	 * @param Node $rootNode
+	 * @param Element $rootNode
 	 * @return int
 	 */
-	public static function getIndentLevel( Node $node, Node $rootNode ): int {
+	public static function getIndentLevel( Node $node, Element $rootNode ): int {
 		$indent = 0;
 		while ( $node ) {
 			if ( $node === $rootNode ) {
 				break;
 			}
-			$nodeName = strtolower( $node->nodeName );
-			if ( $nodeName === 'li' || $nodeName === 'dd' ) {
+			$tagName = $node instanceof Element ? strtolower( $node->tagName ) : null;
+			if ( $tagName === 'li' || $tagName === 'dd' ) {
 				$indent++;
 			}
 			$node = $node->parentNode;
diff --git a/includes/ThreadItem.php b/includes/ThreadItem.php
index 8ac47de9e..7f7035f5f 100644
--- a/includes/ThreadItem.php
+++ b/includes/ThreadItem.php
@@ -7,7 +7,6 @@ use LogicException;
 use Title;
 use Wikimedia\Assert\Assert;
 use Wikimedia\Parsoid\DOM\Element;
-use Wikimedia\Parsoid\DOM\Node;
 use Wikimedia\Parsoid\Utils\DOMUtils;
 
 /**
@@ -337,9 +336,9 @@ abstract class ThreadItem implements JsonSerializable {
 	}
 
 	/**
-	 * @return Node Root node (level is relative to this node)
+	 * @return Element Root node (level is relative to this node)
 	 */
-	public function getRootNode(): Node {
+	public function getRootNode(): Element {
 		return $this->rootNode;
 	}
 
@@ -400,9 +399,9 @@ abstract class ThreadItem implements JsonSerializable {
 	}
 
 	/**
-	 * @param Node $rootNode Root node (level is relative to this node)
+	 * @param Element $rootNode Root node (level is relative to this node)
 	 */
-	public function setRootNode( Node $rootNode ): void {
+	public function setRootNode( Element $rootNode ): void {
 		$this->rootNode = $rootNode;
 	}
 
diff --git a/modules/utils.js b/modules/utils.js
index d5c61a6a0..d910a8d7c 100644
--- a/modules/utils.js
+++ b/modules/utils.js
@@ -280,7 +280,7 @@ function htmlTrim( str ) {
  *
  * @private
  * @param {Node} node
- * @param {Node} rootNode
+ * @param {Element} rootNode
  * @return {number}
  */
 function getIndentLevel( node, rootNode ) {
@@ -289,7 +289,7 @@ function getIndentLevel( node, rootNode ) {
 		if ( node === rootNode ) {
 			break;
 		}
-		var tagName = node.tagName && node.tagName.toLowerCase();
+		var tagName = node instanceof HTMLElement ? node.tagName.toLowerCase() : null;
 		if ( tagName === 'li' || tagName === 'dd' ) {
 			indent++;
 		}