Document Py_RETURN_NONE.
diff --git a/Doc/api/concrete.tex b/Doc/api/concrete.tex
index b00b915..7ad6e91 100644
--- a/Doc/api/concrete.tex
+++ b/Doc/api/concrete.tex
@@ -97,6 +97,10 @@
   with respect to reference counts.
 \end{cvardesc}
 
+\begin{csimplemacrodesc}{Py_RETURN_NONE}
+  Properly handles returning \cvar{Py_None} from within a C function.
+\end{csimplemacrodesc}
+
 
 \section{Numeric Objects \label{numericObjects}}