document OverflowError exception on mktime()
diff --git a/Doc/lib/libtime.tex b/Doc/lib/libtime.tex
index 56488d1..f91a492 100644
--- a/Doc/lib/libtime.tex
+++ b/Doc/lib/libtime.tex
@@ -86,7 +86,8 @@
\begin{funcdesc}{mktime}{tuple}
This is the inverse function of \code{localtime}. Its argument is the
-full 9-tuple (since the dst flag is needed). It returns an integer.
+full 9-tuple (since the dst flag is needed). It returns an integer. If the
+input value can't be represented as a non-negative integer, OverflowError is raised.
\end{funcdesc}
\begin{funcdesc}{sleep}{secs}