diff --git a/doc/conf.py b/doc/conf.py
index aa934f233bb5..d4b2d30f24d3 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -366,6 +366,8 @@ def _check_dependencies():
 
 html4_writer = True
 
+inheritance_node_attrs = dict(fontsize=16)
+
 
 def setup(app):
     if any(st in version for st in ('post', 'alpha', 'beta')):