1 files changed, 6 insertions, 0 deletions
diff --git a/mdoc.7 b/mdoc.7
index bb9f8cb0..3f25dff3 100644
--- a/mdoc.7
+++ b/mdoc.7
@@ -1960,6 +1960,12 @@ and
 .Sx \&Ex
 macros were stipulated only to occur in certain manual sections.
 mandoc does not have these restrictions.
+.It
+Newer groff and mandoc print
+.Qq AT&T UNIX
+prior to unknown arguments of
+.Sx \&At ;
+older groff did nothing.
 .El
 .Sh SEE ALSO
 .Xr mandoc 1 ,