diff --git a/docs/extensiondev.rst b/docs/extensiondev.rst
index 8b18e726..5b20528e 100644
--- a/docs/extensiondev.rst
+++ b/docs/extensiondev.rst
@@ -386,7 +386,7 @@ extension to be approved you have to follow these guidelines:
    themes for Sphinx documentation.
 8. The ``zip_safe`` flag in the setup script must be set to ``False``,
    even if the extension would be safe for zipping.
-9. An extension currently has to support Python 2.7.
+9. An extension currently has to support Python 2.7, Python 3.3 and higher.
 
 
 .. _ext-import-transition: