diff --git a/src/saveload/saveload.h b/src/saveload/saveload.h
--- a/src/saveload/saveload.h
+++ b/src/saveload/saveload.h
@@ -340,6 +340,7 @@ enum SaveLoadVersion : uint16 {
 	SLV_LINKGRAPH_TRAVEL_TIME,              ///< 297  PR#9457 v12.0-RC1  Store travel time in the linkgraph.
 	SLV_DOCK_DOCKINGTILES,                  ///< 298  PR#9578 All tiles around docks may be docking tiles.
 	SLV_REPAIR_OBJECT_DOCKING_TILES,        ///< 299  PR#9594 v12.0  Fixing issue with docking tiles overlapping objects.
+	SLV_U64_TICK_COUNTER,                   ///< 300  PR#10035 Make _tick_counter 64bit to avoid wrapping.
 
 	SL_MAX_VERSION,                         ///< Highest possible saveload version
 };