diff --git a/book/source/conf.py b/book/source/conf.py
index 63b6dcd..2f9972d 100644
--- a/book/source/conf.py
+++ b/book/source/conf.py
@@ -48,6 +48,9 @@ epub_css_files = [
 
 html_theme = 'alabaster'
 html_static_path = ['_static']
+html_css_files = [
+    ('html/css/custom.css', {'priority': 1000})
+]
 
 html_show_sphinx = False
 html_show_copyright = False