diff --git a/apps/web/src/components/settings/NoteProseCssPreview.tsx b/apps/web/src/components/settings/NoteProseCssPreview.tsx
index 96d0f25a..2c756a01 100644
--- a/apps/web/src/components/settings/NoteProseCssPreview.tsx
+++ b/apps/web/src/components/settings/NoteProseCssPreview.tsx
@@ -89,14 +89,21 @@ export const NoteProseCssPreview = ({
     anchor.textContent = link;
     const codeElement = document.createElement("code");
     codeElement.textContent = code;
-    paragraph.append(before, anchor, between, codeElement, after);
+    // Root typecheck resolves ParentNode.append to the Workers stream helper.
+    paragraph.appendChild(document.createTextNode(before));
+    paragraph.appendChild(anchor);
+    paragraph.appendChild(document.createTextNode(between));
+    paragraph.appendChild(codeElement);
+    paragraph.appendChild(document.createTextNode(after));
     const quotation = document.createElement("blockquote");
     const quotationText = document.createElement("p");
     quotationText.textContent = quote;
-    quotation.append(quotationText);
-    prose.append(title, paragraph, quotation);
-    frame.append(prose);
-    scope.append(frame);
+    quotation.appendChild(quotationText);
+    prose.appendChild(title);
+    prose.appendChild(paragraph);
+    prose.appendChild(quotation);
+    frame.appendChild(prose);
+    scope.appendChild(frame);
     root.replaceChildren(style, scope);
   }, [after, before, between, code, dark, fontSize, heading, lineHeight, link, previewCss, quote]);
 
diff --git a/tests/web-sync-queue.test.ts b/tests/web-sync-queue.test.ts
index f2618868..905bd028 100644
--- a/tests/web-sync-queue.test.ts
+++ b/tests/web-sync-queue.test.ts
@@ -15,6 +15,7 @@ const {
 } = await import("../apps/web/src/lib/sync-queue");
 const { formatLocalDraftClipboardText } = await import("../apps/web/src/lib/memo-save-conflict");
 const originalFetch = globalThis.fetch;
+const originalNavigator = Object.getOwnPropertyDescriptor(globalThis, "navigator");
 
 const payload = (title: string, revision = 0): MemoUpdateSyncPayload => ({
   memoId: "memo_sync_test",
@@ -76,6 +77,11 @@ beforeEach(async () => {
 
 afterEach(() => {
   globalThis.fetch = originalFetch;
+  if (originalNavigator) {
+    Object.defineProperty(globalThis, "navigator", originalNavigator);
+  } else {
+    delete globalThis.navigator;
+  }
 });
 
 describe("web sync queue concurrency", () => {