diff --git a/docs/source/advanced/chain/index.rst b/docs/source/advanced/chain/index.rst
index 48b556b2e..7cbce0ca0 100644
--- a/docs/source/advanced/chain/index.rst
+++ b/docs/source/advanced/chain/index.rst
@@ -12,4 +12,4 @@ The **chain** mechanism is implemented in xCAT genesis system. The genesis is a
     chain_tasks.rst
     run_tasks_during_discovery.rst
     run_tasks_to_configure.rst
-     
+