diff --git a/Doc/lib/libthread.tex b/Doc/lib/libthread.tex
index 9bc1849b521..c8d251e06e1 100644
--- a/Doc/lib/libthread.tex
+++ b/Doc/lib/libthread.tex
@@ -44,6 +44,7 @@ will cause the thread to exit silently.
 \end{funcdesc}
 
 \begin{funcdesc}{exit_thread}{}
+\deprecated{1.5.2}{Use \function{exit()}.}
 This is an obsolete synonym for \function{exit()}.
 \end{funcdesc}