fix "Title underline too short" sphinx warning
diff --git a/Doc/library/subprocess.rst b/Doc/library/subprocess.rst
index 78fa86c..274a6d9 100644
--- a/Doc/library/subprocess.rst
+++ b/Doc/library/subprocess.rst
@@ -234,7 +234,7 @@
 
 
 Popen Constructor
-^^^^^^^^^^^^^^^^
+^^^^^^^^^^^^^^^^^
 
 The underlying process creation and management in this module is handled by
 the :class:`Popen` class. It offers a lot of flexibility so that developers