diff --git a/src/saveload/afterload.cpp b/src/saveload/afterload.cpp
--- a/src/saveload/afterload.cpp
+++ b/src/saveload/afterload.cpp
@@ -3111,6 +3111,13 @@ bool AfterLoadGame()
 		FOR_ALL_INDUSTRIES(ind) if (ind->neutral_station != NULL) ind->neutral_station->industry = ind;
 	}
 
+	{
+		/* Update water class for trees for all current savegame versions. */
+		for (TileIndex t = 0; t < map_size; t++) {
+			if (IsTileType(t, MP_TREES)) SetWaterClass(t, GetTreeGround(t) == TREE_GROUND_SHORE ? WATER_CLASS_SEA : WATER_CLASS_INVALID);
+		}
+	}
+
 	/* Compute station catchment areas. This is needed here in case UpdateStationAcceptance is called below. */
 	Station::RecomputeCatchmentForAll();
 
diff --git a/src/tree_map.h b/src/tree_map.h
--- a/src/tree_map.h
+++ b/src/tree_map.h
@@ -277,6 +277,7 @@ static inline void MakeTree(TileIndex t,
 {
 	SetTileType(t, MP_TREES);
 	SetTileOwner(t, OWNER_NONE);
+	SetWaterClass(t, ground == TREE_GROUND_SHORE ? WATER_CLASS_SEA : WATER_CLASS_INVALID);
 	_m[t].m2 = ground << 6 | density << 4 | 0;
 	_m[t].m3 = type;
 	_m[t].m4 = 0 << 5 | 0 << 2;