diff --git a/doc/manual-src/en/conf.py.in b/doc/manual-src/en/conf.py.in
index f9815f13..87512006 100644
--- a/doc/manual-src/en/conf.py.in
+++ b/doc/manual-src/en/conf.py.in
@@ -101,7 +101,7 @@ html_theme_options = {'bodyfont':'roboto, sans-serif',
                       'relbarbgcolor':'#fff',
                       'relbartextcolor':'#444',
                       'relbarlinkcolor':'#444',
-                      'sidebarbgcolor':'none',
+                      'sidebarbgcolor':'#eee',
                       'sidebartextcolor':'#444',
                       'sidebarlinkcolor':'#444',
                       'headbgcolor':'none',