diff --git a/doc/conf.py b/doc/conf.py
index d0db2a953..be577e8b0 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -46,13 +46,8 @@
 # see https://github.com/numpy/numpydoc/issues/69
 numpydoc_show_class_members = False
 
-# pngmath / imgmath compatibility layer for different sphinx versions
-import sphinx
-from distutils.version import LooseVersion
-if LooseVersion(sphinx.__version__) < LooseVersion('1.4'):
-    extensions.append('sphinx.ext.pngmath')
-else:
-    extensions.append('sphinx.ext.imgmath')
+extensions.append('sphinx.ext.imgmath')
+imgmath_image_format = 'svg'
 
 autodoc_default_flags = ['members', 'inherited-members']
 
@@ -138,7 +133,7 @@
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the
 # documentation.
-# html_theme_options = {'prev_next_buttons_location': None}
+# html_theme_options = {}
 
 # Add any paths that contain custom themes here, relative to this directory.
 html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]