diff --git a/src/core/strong_typedef_type.hpp b/src/core/strong_typedef_type.hpp
index e1baeee311..4493545358 100644
--- a/src/core/strong_typedef_type.hpp
+++ b/src/core/strong_typedef_type.hpp
@@ -127,8 +127,8 @@ namespace StrongType {
 			friend constexpr bool operator >=(const TType &lhs, TCompatibleType rhs) { return lhs.value >= static_cast<TBaseType>(rhs); }
 			friend constexpr bool operator >(const TType &lhs, TCompatibleType rhs) { return lhs.value > static_cast<TBaseType>(rhs); }
 
-			friend constexpr TType operator +(const TType &lhs, TCompatibleType rhs) { return { static_cast<TBaseType>(lhs.value + rhs) }; }
-			friend constexpr TType operator -(const TType &lhs, TCompatibleType rhs) { return { static_cast<TBaseType>(lhs.value - rhs) }; }
+			friend constexpr TType operator +(const TType &lhs, TCompatibleType rhs) { return TType{ static_cast<TBaseType>(lhs.value + rhs) }; }
+			friend constexpr TType operator -(const TType &lhs, TCompatibleType rhs) { return TType{ static_cast<TBaseType>(lhs.value - rhs) }; }
 		};
 	};
 
@@ -154,7 +154,7 @@ namespace StrongType {
 		constexpr Typedef(const Typedef &) = default;
 		constexpr Typedef(Typedef &&) = default;
 
-		constexpr Typedef(const TBaseType &value) : value(value) {}
+		explicit constexpr Typedef(const TBaseType &value) : value(value) {}
 
 		constexpr Typedef &operator =(const Typedef &rhs) { this->value = rhs.value; return *this; }
 		constexpr Typedef &operator =(Typedef &&rhs) { this->value = std::move(rhs.value); return *this; }
diff --git a/src/map_func.h b/src/map_func.h
index cde6d7628e..3c94925831 100644
--- a/src/map_func.h
+++ b/src/map_func.h
@@ -442,6 +442,9 @@ inline TileIndexDiff ToTileIndexDiff(TileIndexDiffC tidc)
 	return TileDiffXY(tidc.x, tidc.y);
 }
 
+/* Helper functions to provide explicit +=/-= operators for TileIndex and TileIndexDiff. */
+constexpr TileIndex &operator+=(TileIndex &tile, TileIndexDiff offset) { tile = tile + TileIndex(offset); return tile; }
+constexpr TileIndex &operator-=(TileIndex &tile, TileIndexDiff offset) { tile = tile - TileIndex(offset); return tile; }
 
 /**
  * Adds a given offset to a tile.
diff --git a/src/saveload/town_sl.cpp b/src/saveload/town_sl.cpp
index 9299330cc4..32f2cd8520 100644
--- a/src/saveload/town_sl.cpp
+++ b/src/saveload/town_sl.cpp
@@ -76,7 +76,7 @@ void UpdateHousesAndTowns()
 	}
 
 	/* Check for cases when a NewGRF has set a wrong house substitute type. */
-	for (const auto t : Map::Iterate()) {
+	for (const TileIndex &t : Map::Iterate()) {
 		if (!IsTileType(t, MP_HOUSE)) continue;
 
 		HouseID house_type = GetCleanHouseType(t);