diff --git a/man3/termios.3 b/man3/termios.3
index 57f916ede..1bc8add18 100644
--- a/man3/termios.3
+++ b/man3/termios.3
@@ -241,7 +241,10 @@ or
 .TP
 .B TABDLY
 Horizontal tab delay mask.
-Values are \fBTAB0\fP, \fBTAB1\fP, \fBTAB2\fP, \fBTAB3\fP (or \fBXTABS\fP).
+Values are \fBTAB0\fP, \fBTAB1\fP, \fBTAB2\fP, \fBTAB3\fP (or \fBXTABS\fP,
+but see the
+.B BUGS
+section).
 A value of TAB3, that is, XTABS, expands tabs to spaces
 (with tab stops every eight columns).
 [requires
@@ -1085,6 +1088,19 @@ behaves like
 .\" libc4.7.6, libc5, glibc for unix: duration in ms.
 .\" glibc for bsd: duration in us
 .\" glibc for sunos4: ignore duration
+.SH BUGS
+.\" kernel 77e5bff1640432f28794a00800955e646dcd7455
+.\" glibc 573963e32ffac46d9891970ddebde2ac3212c5c0
+On alpha, Linux before 4.16 (and glibc before 2.28) had
+.B XTABS
+value different from
+.B TAB3
+and it was ignored by the
+.B N_TTY
+line discipline code of the tty driver as a result
+(as it wasn't a part of the
+.B TABDLY
+mask).
 .SH SEE ALSO
 .BR reset (1),
 .BR setterm (1),