diff --git a/src/town.h b/src/town.h
--- a/src/town.h
+++ b/src/town.h
@@ -340,7 +340,7 @@ static inline Town *GetRandomTown()
 	return GetTown(index);
 }
 
-Town *CalcClosestTownFromTile(TileIndex tile, uint threshold);
+Town *CalcClosestTownFromTile(TileIndex tile, uint threshold = UINT_MAX);
 
 #define FOR_ALL_TOWNS_FROM(t, start) for (t = GetTown(start); t != NULL; t = (t->index + 1U < GetTownPoolSize()) ? GetTown(t->index + 1U) : NULL) if (t->IsValid())
 #define FOR_ALL_TOWNS(t) FOR_ALL_TOWNS_FROM(t, 0)