diff --git a/Doc/api/exceptions.tex b/Doc/api/exceptions.tex
index f98b644..3a51a05 100644
--- a/Doc/api/exceptions.tex
+++ b/Doc/api/exceptions.tex
@@ -299,12 +299,14 @@
 \end{cfuncdesc}
 
 \begin{cfuncdesc}{void}{PyErr_SetInterrupt}{}
-  This function is obsolete.  It simulates the effect of a
+  It simulates the effect of a
   \constant{SIGINT}\ttindex{SIGINT} signal arriving --- the next time
   \cfunction{PyErr_CheckSignals()} is called,
   \withsubitem{(built-in exception)}{\ttindex{KeyboardInterrupt}}
   \exception{KeyboardInterrupt} will be raised.  It may be called
   without holding the interpreter lock.
+  % XXX This was described as obsolete, but is used in
+  % thread.interrupt_main() (used from IDLE), so it's still needed.
 \end{cfuncdesc}
 
 \begin{cfuncdesc}{PyObject*}{PyErr_NewException}{char *name,