diff --git a/man2/signalfd.2 b/man2/signalfd.2
index 47eebaaa9..b42266311 100644
--- a/man2/signalfd.2
+++ b/man2/signalfd.2
@@ -335,6 +335,14 @@ If a signal appears in the
 of more than one of the file descriptors, then occurrences
 of that signal can be read (once) from any one of the file descriptors.
 
+Attempts to include
+.B SIGKILL
+and
+.B SIGSTOP
+in
+.I mask
+are silently ignored.
+
 The signal mask employed by a signalfd file descriptor can be viewed
 via the entry for the corresponding file descriptor in the process's
 .IR /proc/[pid]/fdinfo