diff --git a/src/contentScript/sidebarDomControllerLite.ts b/src/contentScript/sidebarDomControllerLite.ts
index e9136d7f5d..29301cb988 100644
--- a/src/contentScript/sidebarDomControllerLite.ts
+++ b/src/contentScript/sidebarDomControllerLite.ts
@@ -29,8 +29,9 @@ import { uuidv4 } from "@/types/helpers";
 export const SIDEBAR_WIDTH_CSS_PROPERTY = "--pb-sidebar-width";
 const ORIGINAL_MARGIN_CSS_PROPERTY = "--pb-original-margin-right";
 
+// Use ? because it's somehow not defined in e2e tests. But otherwise it will always be defined.
 // eslint-disable-next-line local-rules/persistBackgroundData -- Static
-const html: HTMLElement = globalThis.document.documentElement;
+const html: HTMLElement = globalThis.document?.documentElement;
 const SIDEBAR_WIDTH_PX = 400;
 
 function storeOriginalCSSOnce() {