diff --git a/docs/conf.py b/docs/conf.py
index 9f31529..d7d2ad2 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -34,7 +34,6 @@ extensions = [
     'sphinx.ext.intersphinx',
     'sphinx.ext.todo',
     'sphinx.ext.coverage',
-    'sphinx.ext.pngmath',
     'sphinx.ext.viewcode',
 ]