diff --git a/doc/index.rst b/doc/index.rst
index 1f11070b87f399289b4645ad93e5fdf6232e65f8_ZG9jL2luZGV4LnJzdA==..762c368eae42131cce0ffea2b1d4f48ea0fd5a11_ZG9jL2luZGV4LnJzdA== 100644
--- a/doc/index.rst
+++ b/doc/index.rst
@@ -5,6 +5,12 @@
 It is pure Python and about twice as slow than lxml or other solutions.
 
 
+Note on performance
+-------------------
+
+There is one area where an optimisation for lxml will negatively affect the performance of et_xmfile: when using the `.element()` method on an xmlfile context manager. It is recommended not to use this, though the method is provided for code compatibility.
+
+
 Sample code:
 ++++++++++++
 
@@ -12,7 +18,7 @@
 
 
 API Documentation
-------------------
+-----------------
 
 .. toctree::
     :maxdepth: 1