diff --git a/doc/builtin/signal b/doc/builtin/signal
index eadd0008fc23ede12d2b8f4361461f6796bcfde3..5fe23bc839ec623b95d17d0a6f880682630e63cf 100644
--- a/doc/builtin/signal
+++ b/doc/builtin/signal
@@ -19,5 +19,7 @@ DESCRIPTION
 	If no second argument is given, the signal handler for that signal
 	is restored to the default handler.
 
+	If the second argument is zero, the signal will be completely ignored.
+
 SEE ALSO
 	kill, signame, signum