diff --git a/extension.json b/extension.json
index 7c229139..adcefcb8 100644
--- a/extension.json
+++ b/extension.json
@@ -14,7 +14,7 @@
 	"license-name": "GPL-2.0-or-later",
 	"type": "parserhook",
 	"requires": {
-		"MediaWiki": ">= 1.33",
+		"MediaWiki": ">= 1.34",
 		"platform": {
 			"ability-shell": true
 		}
diff --git a/includes/SyntaxHighlight.php b/includes/SyntaxHighlight.php
index 3ed48f0a..748b1125 100644
--- a/includes/SyntaxHighlight.php
+++ b/includes/SyntaxHighlight.php
@@ -121,7 +121,9 @@ class SyntaxHighlight {
 		$out = $result->getValue();
 
 		// Allow certain HTML attributes
-		$htmlAttribs = Sanitizer::validateAttributes( $args, [ 'style', 'class', 'id', 'dir' ] );
+		$htmlAttribs = Sanitizer::validateAttributes(
+			$args, array_flip( [ 'style', 'class', 'id', 'dir' ] )
+		);
 		if ( !isset( $htmlAttribs['class'] ) ) {
 			$htmlAttribs['class'] = self::HIGHLIGHT_CSS_CLASS;
 		} else {