From 5b0bb8c1e14a940b88b5048b0a4141e938fc597d Mon Sep 17 00:00:00 2001
From: shimizukawa <shimizukawa@gmail.com>
Date: Sun, 15 Feb 2015 18:01:43 +0900
Subject: [PATCH] Fix bug refs #1722. Circler toctree cause infinite loop.

---
 sphinx/environment.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sphinx/environment.py b/sphinx/environment.py
index 535d714cf..676899670 100644
--- a/sphinx/environment.py
+++ b/sphinx/environment.py
@@ -1297,7 +1297,7 @@ class BuildEnvironment:
                 parent[child] = p
         ancestors = []
         d = docname
-        while d in parent:
+        while d in parent and d not in ancestors:
             ancestors.append(d)
             d = parent[d]
         return ancestors