diff --git a/src/Makefile.in b/src/Makefile.in
index e622ade931e..15ca1667d65 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -170,7 +170,7 @@ NOTIFY_LIBS = @NOTIFY_LIBS@
 
 ## -ltermcap, or -lncurses, or -lcurses, or "".
 LIBS_TERMCAP=@LIBS_TERMCAP@
-## terminfo.o if TERMINFO, else tparam.o.
+## terminfo.o if TERMINFO, else (on MS-DOS only: termcap.o +) tparam.o.
 TERMCAP_OBJ=@TERMCAP_OBJ@
 
 LIBXMU=@LIBXMU@
diff --git a/src/termcap.c b/src/termcap.c
index ee0b8f5cbb6..4d85323a9ef 100644
--- a/src/termcap.c
+++ b/src/termcap.c
@@ -15,6 +15,9 @@ GNU General Public License for more details.
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
 
+/* Since 2010-03, 073589f4, Emacs 24.1, this file is only used
+   by the MS-DOS port of Emacs.  */
+
 /* Emacs config.h may rename various library functions such as malloc.  */
 #include <config.h>
 #include <sys/file.h>