diff --git a/man7/signal.7 b/man7/signal.7
index ce52f88fb..abc3bea7e 100644
--- a/man7/signal.7
+++ b/man7/signal.7
@@ -446,6 +446,26 @@ resource limit, which specifies a per-user limit for queued
 signals; see
 .BR setrlimit (2)
 for further details.
+
+The addition or real-time signals required the widening
+of the signal set structure
+.RI ( sigset_t )
+from 32 to 64 bits.
+Consequently, various system calls were superseded by new system calls
+that supported the larger signal sets.
+The old and new system calls are as follows:
+.TS
+lb lb
+l l.
+Linux 2.0 and earlier	Linux 2.2 and later
+\fBsigaction\fP(2)	\fBrt_sigaction\fP(2)
+\fBsigpending\fP(2)	\fBrt_sigpending\fP(2)
+\fBsigprocmask\fP(2)	\fBrt_sigprocmask\fP(2)
+\fBsigreturn\fP(2)	\fBrt_sigreturn\fP(2)
+\fBsigsuspend\fP(2)	\fBrt_sigsuspend\fP(2)
+\fBsigtimedwait\fP(2)	\fBrt_sigtimedwait\fP(2)
+.TE
+.\"
 .SS Async-signal-safe functions
 .PP
 A signal handler function must be very careful,