diff --git a/config.h.in b/config.h.in
index 1e97f97e74c..6753327247a 100644
--- a/config.h.in
+++ b/config.h.in
@@ -590,6 +590,9 @@
 /* Define if you have the <sys/lock.h> header file.  */
 #undef HAVE_SYS_LOCK_H
 
+/* Define if you have the <sys/modem.h> header file.  */
+#undef HAVE_SYS_MODEM_H
+
 /* Define if you have the <sys/ndir.h> header file.  */
 #undef HAVE_SYS_NDIR_H
 
diff --git a/configure.in b/configure.in
index c17ead759ba..890aae2bd05 100644
--- a/configure.in
+++ b/configure.in
@@ -381,7 +381,7 @@ dnl AC_MSG_RESULT($cpp_type)
 AC_HEADER_STDC
 AC_CHECK_HEADERS(dlfcn.h fcntl.h limits.h locale.h ncurses.h poll.h pthread.h \
 signal.h stdarg.h stddef.h stdlib.h thread.h unistd.h utime.h termios.h \
-sys/audioio.h sys/file.h sys/lock.h db_185.h db.h \
+sys/audioio.h sys/file.h sys/lock.h sys/modem.h db_185.h db.h \
 sys/param.h sys/select.h sys/socket.h sys/time.h sys/times.h \
 sys/un.h sys/utsname.h sys/wait.h pty.h libutil.h \
 ndbm.h db1/ndbm.h gdbm/ndbm.h)