diff --git a/tmk_core/common/keycode.h b/tmk_core/common/keycode.h
index 734c9fbff..9cb4f1e0c 100644
--- a/tmk_core/common/keycode.h
+++ b/tmk_core/common/keycode.h
@@ -17,7 +17,8 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 /*
  * Keycodes based on HID Usage Keyboard/Keypad Page(0x07) plus special codes
- * http://www.usb.org/developers/devclass_docs/Hut1_12.pdf
+ * https://web.archive.org/web/20060218214400/http://www.usb.org/developers/devclass_docs/Hut1_12.pdf
+ * or http://www.usb.org/developers/hidpage/Hut1_12v2.pdf (older)
  */
 #ifndef KEYCODE_H
 #define KEYCODE_H