diff --git a/src/vs/workbench/contrib/markdown/browser/markdownDocumentRenderer.ts b/src/vs/workbench/contrib/markdown/browser/markdownDocumentRenderer.ts
index 60a23a1375e..c836c225451 100644
--- a/src/vs/workbench/contrib/markdown/browser/markdownDocumentRenderer.ts
+++ b/src/vs/workbench/contrib/markdown/browser/markdownDocumentRenderer.ts
@@ -177,6 +177,7 @@ function sanitize(documentContent: string, sanitizerConfig: MarkdownDocumentSani
 				...allowedMarkdownHtmlAttributes,
 				'name',
 				'id',
+				'class',
 				'role',
 				'tabindex',
 				'placeholder',