Document the correct return type of PyLong_AsUnsignedLongLongMask.
diff --git a/Doc/api/concrete.tex b/Doc/api/concrete.tex
index f1fbccb..33d18cd 100644
--- a/Doc/api/concrete.tex
+++ b/Doc/api/concrete.tex
@@ -376,7 +376,7 @@
\versionadded{2.3}
\end{cfuncdesc}
-\begin{cfuncdesc}{unsigned long}{PyLong_AsUnsignedLongLongMask}{PyObject *io}
+\begin{cfuncdesc}{unsigned PY_LONG_LONG}{PyLong_AsUnsignedLongLongMask}{PyObject *io}
Return a C \ctype{unsigned long long} from a Python long integer, without
checking for overflow.
\versionadded{2.3}