diff --git a/src/wp-includes/html-api/class-wp-css-selectors.php b/src/wp-includes/html-api/class-wp-css-selectors.php
index 01e3253893d57..3e35a383b4446 100644
--- a/src/wp-includes/html-api/class-wp-css-selectors.php
+++ b/src/wp-includes/html-api/class-wp-css-selectors.php
@@ -584,7 +584,7 @@ public function matches( WP_HTML_Processor $processor ): bool {
 
 final class WP_CSS_Class_Selector extends WP_CSS_Selector_Parser {
 	public function matches( WP_HTML_Processor $processor ): bool {
-		return $processor->has_class( $this->ident );
+		return (bool) $processor->has_class( $this->ident );
 	}
 
 	/** @var string */