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}
diff --git a/Doc/libtime.tex b/Doc/libtime.tex
index 56488d1..f91a492 100644
--- a/Doc/libtime.tex
+++ b/Doc/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}