diff --git a/doc/conf.py b/doc/conf.py
index f88ff6afd..d3d828145 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -23,10 +23,10 @@
 
 # Add any Sphinx extension module names here, as strings. They can be extensions
 # coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
-extensions = ['matplotlib.sphinxext.mathmpl', 'math_symbol_table',
+extensions = ['matplotlib.sphinxext.mathmpl',
               'sphinx.ext.autodoc', 'matplotlib.sphinxext.only_directives',
-              'matplotlib.sphinxext.plot_directive', 'inheritance_diagram',
-              'gen_rst',
+              'matplotlib.sphinxext.plot_directive',
+              'sphinx.ext.inheritance_diagram',
               'matplotlib.sphinxext.ipython_console_highlighting']
 
 # Add any paths that contain templates here, relative to this directory.