diff --git a/newgrf.c b/newgrf.c
index 9e4b55ec9a..3eb3728278 100644
--- a/newgrf.c
+++ b/newgrf.c
@@ -2218,6 +2218,9 @@ static uint32 GetParamVal(byte param, uint32 *cond_val)
 		case 0x92: /* Game mode */
 			return _game_mode;
 
+		case 0x9A: /* Always -1 */
+			return -1;
+
 		case 0x9D: /* TTD Platform, 00=TTDPatch, 01=OpenTTD */
 			return 1;