diff --git a/doc/groff.texi b/doc/groff.texi
index a8ee81643..a5c4e648c 100644
--- a/doc/groff.texi
+++ b/doc/groff.texi
@@ -3496,7 +3496,8 @@ normally precedes each heading is omitted.
 After @code{NH} is called, the assigned number is made available in the
 strings @code{SN-DOT} (as it appears in a printed heading with default
 formatting, followed by a terminating period) and @code{SN-NO-DOT} (with
-the terminating period omitted).  These are GNU extensions.
+the terminating period omitted).  These (and @code{SN-STYLE}) are GNU
+extensions.
 
 You can control the style used to print numbered headings by defining an
 appropriate alias for the string @code{SN-STYLE}.  By default,
diff --git a/doc/ms.ms b/doc/ms.ms
index 5487aea07..aa9ca72d2 100644
--- a/doc/ms.ms
+++ b/doc/ms.ms
@@ -1336,7 +1336,10 @@ and
 .CW SN\-NO\-DOT
 (with the terminating period omitted).
 .
-These are GNU extensions.
+These,
+and
+.CW SN\-STYLE ,
+are GNU extensions.
 .
 .
 .PP
diff --git a/tmac/groff_ms.7.man b/tmac/groff_ms.7.man
index ae025399e..6b89eb25b 100644
--- a/tmac/groff_ms.7.man
+++ b/tmac/groff_ms.7.man
@@ -906,7 +906,10 @@ and
 .B SN\-NO\-DOT
 (with the terminating period omitted).
 .
-These are GNU extensions.
+These,
+and
+.BR SN\-STYLE ,
+are GNU extensions.
 .
 .
 .P