diff --git a/man3/pthread_tryjoin_np.3 b/man3/pthread_tryjoin_np.3
index 86fdc5188..48daaa222 100644
--- a/man3/pthread_tryjoin_np.3
+++ b/man3/pthread_tryjoin_np.3
@@ -63,7 +63,10 @@ If
 .I thread
 has not yet terminated,
 then the call blocks until a maximum time, specified in
-.IR abstime .
+.IR abstime ,
+measured against the
+.BR CLOCK_REALTIME
+clock.
 If the timeout expires before
 .I thread
 terminates,
@@ -157,6 +160,18 @@ if (s != 0) {
 }
 .EE
 .in
+.SH BUGS
+The
+.BR pthread_timedjoin_np ()
+function measures time by internally calculating a relative sleep interval
+that is then measured against the
+.BR CLOCK_MONOTONIC
+clock instead of the
+.BR CLOCK_REALTIME
+clock.
+Consequently, the timeout is unaffected by discontinuous changes to the
+.BR CLOCK_REALTIME
+clock.
 .SH SEE ALSO
 .BR clock_gettime (2),
 .BR pthread_exit (3),