diff --git a/client/src/templates/Challenges/classic/editor.tsx b/client/src/templates/Challenges/classic/editor.tsx
index 8f8a902610..c819342279 100644
--- a/client/src/templates/Challenges/classic/editor.tsx
+++ b/client/src/templates/Challenges/classic/editor.tsx
@@ -907,8 +907,8 @@ const Editor = (props: EditorProps): JSX.Element => {
     if (!previewOpen && showProjectPreview) {
       const description = document.getElementsByClassName(
         'description-container'
-      )[0];
-      description.classList.add('description-highlighter');
+      )?.[0];
+      description?.classList.add('description-highlighter');
     }
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [props.previewOpen]);