diff --git a/aclocal/ax_lua.m4 b/aclocal/ax_lua.m4
index 9feb352..5920167 100644
--- a/aclocal/ax_lua.m4
+++ b/aclocal/ax_lua.m4
@@ -1,5 +1,5 @@
 # ===========================================================================
-#          http://www.gnu.org/software/autoconf-archive/ax_lua.html
+#          https://www.gnu.org/software/autoconf-archive/ax_lua.html
 # ===========================================================================
 #
 # SYNOPSIS
@@ -166,7 +166,7 @@
 #   Public License for more details.
 #
 #   You should have received a copy of the GNU General Public License along
-#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#   with this program. If not, see <https://www.gnu.org/licenses/>.
 #
 #   As a special exception, the respective Autoconf Macro's copyright owner
 #   gives unlimited permission to copy, distribute and modify the configure
@@ -181,7 +181,7 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 39
+#serial 40
 
 dnl =========================================================================
 dnl AX_PROG_LUA([MINIMUM-VERSION], [TOO-BIG-VERSION],