diff --git a/examples/site-to-markdown/main.py b/examples/site-to-markdown/main.py
index 1ff7ade5..65f89d37 100644
--- a/examples/site-to-markdown/main.py
+++ b/examples/site-to-markdown/main.py
@@ -30,11 +30,18 @@ async def site_to_markdown():
             await page.screenshot(full_page=False, type='png')
         ).decode('utf-8')
 
+    # Base64-encode the HTML before injecting into the f-string so that
+    # triple-quote sequences, backslashes, or closing-string markers in
+    # the page content cannot break out of the generated Python source.
+    html_b64 = base64.b64encode(html.encode("utf-8")).decode("utf-8")
+
     # Jupyter: Run code in sandbox to convert html to markdown
     c.jupyter.execute_code(
         code=f"""
+import base64
 from markdownify import markdownify
-html = '''{html}'''
+
+html = base64.b64decode("{html_b64}").decode("utf-8")
 screenshot_b64 = "{screenshot_b64}"
 
 md = f"{{markdownify(html)}}\\n\\n![Screenshot](data:image/png;base64,{{screenshot_b64}})"