diff --git a/doc/source/conf.py b/doc/source/conf.py
index dd5d905c860cfc40a7da65c12edee68692708d5d..a9fa4ab4fdb0f1853f3d89ec12ad02c6097ed82b 100644
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -44,7 +44,7 @@ extensions = [
     'sphinx.ext.intersphinx',
     'sphinx.ext.todo',
     'sphinx.ext.coverage',
-    'sphinx.ext.imgmath',
+    'sphinx.ext.pngmath',
     'sphinx.ext.ifconfig',
     'sphinx.ext.viewcode',
     'sphinx.ext.githubpages',