diff --git a/htdocs/core/lib/xcal.lib.php b/htdocs/core/lib/xcal.lib.php
index 40656e5c0c4..67a978ec89c 100644
--- a/htdocs/core/lib/xcal.lib.php
+++ b/htdocs/core/lib/xcal.lib.php
@@ -12,7 +12,7 @@
  * 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 <http://www.gnu.org/licenses/>.
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
  */