diff --git a/src/calibre/ebooks/pdf/html_writer.py b/src/calibre/ebooks/pdf/html_writer.py
index da8bff51d6..8d16d0addb 100644
--- a/src/calibre/ebooks/pdf/html_writer.py
+++ b/src/calibre/ebooks/pdf/html_writer.py
@@ -980,7 +980,7 @@ def add_header_footer(manager, opts, pdf_doc, container, page_number_display_map
'page-break-after': 'always',
'display': 'flex',
'flex-direction': 'column',
- 'height': '100%',
+ 'height': '100vh',
'justify-content': justify,
'margin-left': '{}pt'.format(margins.left),
'margin-right': '{}pt'.format(margins.right),