diff --git a/doc/sphinx/book/app_b_proctitle.rst b/doc/sphinx/book/app_b_proctitle.rst
index 582caf13ba00a0871d93c399538d904d0632ddce..16586b6586aaf8da95874974918f4c343f30e260 100644
--- a/doc/sphinx/book/app_b_proctitle.rst
+++ b/doc/sphinx/book/app_b_proctitle.rst
@@ -2,7 +2,7 @@
 .. highlight:: lua
 
 -------------------------------------------------------------------------------
-                        Appendix B. List of error codes
+                        Appendix B. Process title
 -------------------------------------------------------------------------------
 
 Linux and FreeBSD operating systems allow a running process to modify its title,
diff --git a/doc/sphinx/book/index.rst b/doc/sphinx/book/index.rst
index cd3e153ba22183ad74cdb0414442a86f9d1885aa..832da98e8a1f5a508a3a6711dce5740797fe999c 100644
--- a/doc/sphinx/book/index.rst
+++ b/doc/sphinx/book/index.rst
@@ -3,6 +3,7 @@
 -------------------------------------------------------------------------------
 
 .. toctree::
+    :maxdepth: 2
 
     intro
     box/index
diff --git a/doc/sphinx/conf.py b/doc/sphinx/conf.py
index 714e68649fb3d5be3675b1360b396d45eaf0f68c..ae75b99786e602530abfc0a7d3c12cad22293874 100644
--- a/doc/sphinx/conf.py
+++ b/doc/sphinx/conf.py
@@ -31,7 +31,6 @@ sys.path.insert(0, os.path.abspath('.'))
 
 extensions = [
     'sphinx.ext.todo',
-    'sphinx.ext.mathjax',
     'sphinx.ext.ifconfig',
     'ext.filters',
     'ext.lua'