diff --git a/src/base_station_base.h b/src/base_station_base.h
index f2e2e58843..0c0ad22770 100644
--- a/src/base_station_base.h
+++ b/src/base_station_base.h
@@ -113,7 +113,7 @@ struct BaseStation : StationPool::PoolItem<&_station_pool> {
 	 * @param available will return false if ever the variable asked for does not exist
 	 * @return the value stored in the corresponding variable
 	 */
-	virtual uint32_t GetNewGRFVariable(const struct ResolverObject &object, uint8_t variable, uint8_t parameter, bool *available) const = 0;
+	virtual uint32_t GetNewGRFVariable(const struct ResolverObject &object, uint8_t variable, uint8_t parameter, bool &available) const = 0;
 
 	/**
 	 * Update the coordinated of the sign (as shown in the viewport).
diff --git a/src/newgrf_airport.cpp b/src/newgrf_airport.cpp
index dca77bb3c7..1471f417e2 100644
--- a/src/newgrf_airport.cpp
+++ b/src/newgrf_airport.cpp
@@ -154,14 +154,14 @@ void AirportOverrideManager::SetEntitySpec(AirportSpec *as)
 	}
 }
 
-/* virtual */ uint32_t AirportScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const
+/* virtual */ uint32_t AirportScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const
 {
 	switch (variable) {
 		case 0x40: return this->layout;
 	}
 
 	if (this->st == nullptr) {
-		*available = false;
+		available = false;
 		return UINT_MAX;
 	}
 
diff --git a/src/newgrf_airport.h b/src/newgrf_airport.h
index 21ca905e37..5ac58bc72d 100644
--- a/src/newgrf_airport.h
+++ b/src/newgrf_airport.h
@@ -167,7 +167,7 @@ struct AirportScopeResolver : public ScopeResolver {
 	}
 
 	uint32_t GetRandomBits() const override;
-	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const override;
+	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const override;
 	void StorePSA(uint pos, int32_t value) override;
 };
 
diff --git a/src/newgrf_airporttiles.cpp b/src/newgrf_airporttiles.cpp
index d2a34fb28d..a4adf748a8 100644
--- a/src/newgrf_airporttiles.cpp
+++ b/src/newgrf_airporttiles.cpp
@@ -159,7 +159,7 @@ static uint32_t GetAirportTileIDAtOffset(TileIndex tile, const Station *st, uint
 	return 0xFF << 8 | ats->grf_prop.subst_id; // so just give it the substitute
 }
 
-/* virtual */ uint32_t AirportTileScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const
+/* virtual */ uint32_t AirportTileScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const
 {
 	assert(this->st != nullptr);
 
@@ -194,7 +194,7 @@ static uint32_t GetAirportTileIDAtOffset(TileIndex tile, const Station *st, uint
 
 	Debug(grf, 1, "Unhandled airport tile variable 0x{:X}", variable);
 
-	*available = false;
+	available = false;
 	return UINT_MAX;
 }
 
diff --git a/src/newgrf_airporttiles.h b/src/newgrf_airporttiles.h
index 53f10bab44..34b3669128 100644
--- a/src/newgrf_airporttiles.h
+++ b/src/newgrf_airporttiles.h
@@ -38,7 +38,7 @@ struct AirportTileScopeResolver : public ScopeResolver {
 	}
 
 	uint32_t GetRandomBits() const override;
-	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const override;
+	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const override;
 };
 
 /** Resolver for tiles of an airport. */
diff --git a/src/newgrf_canal.cpp b/src/newgrf_canal.cpp
index 4425ee00ff..b3e725b0d7 100644
--- a/src/newgrf_canal.cpp
+++ b/src/newgrf_canal.cpp
@@ -30,7 +30,7 @@ struct CanalScopeResolver : public ScopeResolver {
 	}
 
 	uint32_t GetRandomBits() const override;
-	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const override;
+	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const override;
 };
 
 /** Resolver object for canals. */
@@ -59,7 +59,7 @@ struct CanalResolverObject : public ResolverObject {
 	return IsTileType(this->tile, MP_WATER) ? GetWaterTileRandomBits(this->tile) : 0;
 }
 
-/* virtual */ uint32_t CanalScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const
+/* virtual */ uint32_t CanalScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const
 {
 	switch (variable) {
 		/* Height of tile */
@@ -102,7 +102,7 @@ struct CanalResolverObject : public ResolverObject {
 
 	Debug(grf, 1, "Unhandled canal variable 0x{:02X}", variable);
 
-	*available = false;
+	available = false;
 	return UINT_MAX;
 }
 
diff --git a/src/newgrf_debug_gui.cpp b/src/newgrf_debug_gui.cpp
index e19ccba54b..18ce097972 100644
--- a/src/newgrf_debug_gui.cpp
+++ b/src/newgrf_debug_gui.cpp
@@ -169,7 +169,7 @@ public:
 	 * @param avail Return whether the variable is available.
 	 * @return The resolved variable's value.
 	 */
-	virtual uint Resolve(uint index, uint var, uint param, bool *avail) const = 0;
+	virtual uint Resolve(uint index, uint var, uint param, bool &avail) const = 0;
 
 	/**
 	 * Used to decide if the PSA needs a parameter or not.
@@ -449,7 +449,7 @@ struct NewGRFInspectWindow : Window {
 			for (const NIVariable *niv = nif->variables; niv->name != nullptr; niv++) {
 				bool avail = true;
 				uint param = HasVariableParameter(niv->var) ? NewGRFInspectWindow::var60params[GetFeatureNum(this->window_number)][niv->var - 0x60] : 0;
-				uint value = nih->Resolve(index, niv->var, param, &avail);
+				uint value = nih->Resolve(index, niv->var, param, avail);
 
 				if (!avail) continue;
 
diff --git a/src/newgrf_engine.cpp b/src/newgrf_engine.cpp
index 4a5abcdce0..b5659581bd 100644
--- a/src/newgrf_engine.cpp
+++ b/src/newgrf_engine.cpp
@@ -412,7 +412,7 @@ static uint32_t PositionHelper(const Vehicle *v, bool consecutive)
 	return chain_before | chain_after << 8 | (chain_before + chain_after + consecutive) << 16;
 }
 
-static uint32_t VehicleGetVariable(Vehicle *v, const VehicleScopeResolver *object, uint8_t variable, uint32_t parameter, bool *available)
+static uint32_t VehicleGetVariable(Vehicle *v, const VehicleScopeResolver *object, uint8_t variable, uint32_t parameter, bool &available)
 {
 	/* Calculated vehicle parameters */
 	switch (variable) {
@@ -935,11 +935,11 @@ static uint32_t VehicleGetVariable(Vehicle *v, const VehicleScopeResolver *objec
 
 	Debug(grf, 1, "Unhandled vehicle variable 0x{:X}, type 0x{:X}", variable, (uint)v->type);
 
-	*available = false;
+	available = false;
 	return UINT_MAX;
 }
 
-/* virtual */ uint32_t VehicleScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const
+/* virtual */ uint32_t VehicleScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const
 {
 	if (this->v == nullptr) {
 		/* Vehicle does not exist, so we're in a purchase list */
@@ -968,7 +968,7 @@ static uint32_t VehicleGetVariable(Vehicle *v, const VehicleScopeResolver *objec
 			case 0xF2: return 0; // Cargo subtype
 		}
 
-		*available = false;
+		available = false;
 		return UINT_MAX;
 	}
 
@@ -1398,7 +1398,7 @@ void FillNewGRFVehicleCache(const Vehicle *v)
 		/* Only resolve when the cache isn't valid. */
 		if (HasBit(v->grf_cache.cache_valid, cache_entry[1])) continue;
 		bool stub;
-		ro.GetScope(VSG_SCOPE_SELF)->GetVariable(cache_entry[0], 0, &stub);
+		ro.GetScope(VSG_SCOPE_SELF)->GetVariable(cache_entry[0], 0, stub);
 	}
 
 	/* Make sure really all bits are set. */
diff --git a/src/newgrf_engine.h b/src/newgrf_engine.h
index a2795a8d2c..88e8e41303 100644
--- a/src/newgrf_engine.h
+++ b/src/newgrf_engine.h
@@ -39,7 +39,7 @@ struct VehicleScopeResolver : public ScopeResolver {
 	void SetVehicle(const Vehicle *v) { this->v = v; }
 
 	uint32_t GetRandomBits() const override;
-	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const override;
+	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const override;
 	uint32_t GetTriggers() const override;
 };
 
diff --git a/src/newgrf_generic.cpp b/src/newgrf_generic.cpp
index 30e3d840fe..f633715fa8 100644
--- a/src/newgrf_generic.cpp
+++ b/src/newgrf_generic.cpp
@@ -41,7 +41,7 @@ struct GenericScopeResolver : public ScopeResolver {
 	{
 	}
 
-	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const override;
+	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const override;
 
 private:
 	bool ai_callback; ///< Callback comes from the AI.
@@ -118,7 +118,7 @@ void AddGenericCallback(uint8_t feature, const GRFFile *file, const SpriteGroup
 	_gcl[feature].push_front(GenericCallback(file, group));
 }
 
-/* virtual */ uint32_t GenericScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const
+/* virtual */ uint32_t GenericScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const
 {
 	if (this->ai_callback) {
 		switch (variable) {
@@ -140,7 +140,7 @@ void AddGenericCallback(uint8_t feature, const GRFFile *file, const SpriteGroup
 
 	Debug(grf, 1, "Unhandled generic feature variable 0x{:02X}", variable);
 
-	*available = false;
+	available = false;
 	return UINT_MAX;
 }
 
diff --git a/src/newgrf_house.cpp b/src/newgrf_house.cpp
index cd90684a53..5cc41c6049 100644
--- a/src/newgrf_house.cpp
+++ b/src/newgrf_house.cpp
@@ -370,7 +370,7 @@ static uint32_t GetDistanceFromNearbyHouse(uint8_t parameter, TileIndex tile, Ho
 /**
  * @note Used by the resolver to get values for feature 07 deterministic spritegroups.
  */
-/* virtual */ uint32_t HouseScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const
+/* virtual */ uint32_t HouseScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const
 {
 	if (this->tile == INVALID_TILE) {
 		/* House does not yet exist, nor is it being planned to exist. Provide some default values intead. */
@@ -394,7 +394,7 @@ static uint32_t GetDistanceFromNearbyHouse(uint8_t parameter, TileIndex tile, Ho
 		}
 
 		Debug(grf, 1, "Unhandled house variable 0x{:X}", variable);
-		*available = false;
+		available = false;
 		return UINT_MAX;
 	}
 
@@ -512,7 +512,7 @@ static uint32_t GetDistanceFromNearbyHouse(uint8_t parameter, TileIndex tile, Ho
 
 	Debug(grf, 1, "Unhandled house variable 0x{:X}", variable);
 
-	*available = false;
+	available = false;
 	return UINT_MAX;
 }
 
diff --git a/src/newgrf_house.h b/src/newgrf_house.h
index a56b5390e8..954417b7a7 100644
--- a/src/newgrf_house.h
+++ b/src/newgrf_house.h
@@ -44,7 +44,7 @@ struct HouseScopeResolver : public ScopeResolver {
 	}
 
 	uint32_t GetRandomBits() const override;
-	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const override;
+	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const override;
 	uint32_t GetTriggers() const override;
 };
 
diff --git a/src/newgrf_industries.cpp b/src/newgrf_industries.cpp
index 7ad754f8d5..bd8fe0084b 100644
--- a/src/newgrf_industries.cpp
+++ b/src/newgrf_industries.cpp
@@ -156,7 +156,7 @@ static uint32_t GetCountAndDistanceOfClosestInstance(uint8_t param_setID, uint8_
 	return count << 16 | GB(closest_dist, 0, 16);
 }
 
-/* virtual */ uint32_t IndustriesScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const
+/* virtual */ uint32_t IndustriesScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const
 {
 	if (this->ro.callback == CBID_INDUSTRY_LOCATION) {
 		/* Variables available during construction check. */
@@ -202,7 +202,7 @@ static uint32_t GetCountAndDistanceOfClosestInstance(uint8_t param_setID, uint8_
 	if (this->industry == nullptr) {
 		Debug(grf, 1, "Unhandled variable 0x{:X} (no available industry) in callback 0x{:x}", variable, this->ro.callback);
 
-		*available = false;
+		available = false;
 		return UINT_MAX;
 	}
 
@@ -411,7 +411,7 @@ static uint32_t GetCountAndDistanceOfClosestInstance(uint8_t param_setID, uint8_
 
 	Debug(grf, 1, "Unhandled industry variable 0x{:X}", variable);
 
-	*available = false;
+	available = false;
 	return UINT_MAX;
 }
 
diff --git a/src/newgrf_industries.h b/src/newgrf_industries.h
index 827302ec5d..f4ac7dab0a 100644
--- a/src/newgrf_industries.h
+++ b/src/newgrf_industries.h
@@ -33,7 +33,7 @@ struct IndustriesScopeResolver : public ScopeResolver {
 	}
 
 	uint32_t GetRandomBits() const override;
-	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const override;
+	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const override;
 	uint32_t GetTriggers() const override;
 	void StorePSA(uint pos, int32_t value) override;
 };
diff --git a/src/newgrf_industrytiles.cpp b/src/newgrf_industrytiles.cpp
index f4c6ce5aeb..bafd2a5731 100644
--- a/src/newgrf_industrytiles.cpp
+++ b/src/newgrf_industrytiles.cpp
@@ -58,7 +58,7 @@ uint32_t GetRelativePosition(TileIndex tile, TileIndex ind_tile)
 	return ((y & 0xF) << 20) | ((x & 0xF) << 16) | (y << 8) | x;
 }
 
-/* virtual */ uint32_t IndustryTileScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const
+/* virtual */ uint32_t IndustryTileScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const
 {
 	switch (variable) {
 		/* Construction state of the tile: a value between 0 and 3 */
@@ -95,7 +95,7 @@ uint32_t GetRelativePosition(TileIndex tile, TileIndex ind_tile)
 
 	Debug(grf, 1, "Unhandled industry tile variable 0x{:X}", variable);
 
-	*available = false;
+	available = false;
 	return UINT_MAX;
 }
 
diff --git a/src/newgrf_industrytiles.h b/src/newgrf_industrytiles.h
index 538c0b7675..e9431edf00 100644
--- a/src/newgrf_industrytiles.h
+++ b/src/newgrf_industrytiles.h
@@ -31,7 +31,7 @@ struct IndustryTileScopeResolver : public ScopeResolver {
 	}
 
 	uint32_t GetRandomBits() const override;
-	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const override;
+	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const override;
 	uint32_t GetTriggers() const override;
 };
 
diff --git a/src/newgrf_object.cpp b/src/newgrf_object.cpp
index 8491c98382..14046a469b 100644
--- a/src/newgrf_object.cpp
+++ b/src/newgrf_object.cpp
@@ -254,7 +254,7 @@ static uint32_t GetCountAndDistanceOfClosestInstance(uint8_t local_id, uint32_t
 }
 
 /** Used by the resolver to get values for feature 0F deterministic spritegroups. */
-/* virtual */ uint32_t ObjectScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const
+/* virtual */ uint32_t ObjectScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const
 {
 	/* We get the town from the object, or we calculate the closest
 	 * town if we need to when there's no object. */
@@ -361,7 +361,7 @@ static uint32_t GetCountAndDistanceOfClosestInstance(uint8_t local_id, uint32_t
 unhandled:
 	Debug(grf, 1, "Unhandled object variable 0x{:X}", variable);
 
-	*available = false;
+	available = false;
 	return UINT_MAX;
 }
 
diff --git a/src/newgrf_object.h b/src/newgrf_object.h
index 2308d100ed..799896f309 100644
--- a/src/newgrf_object.h
+++ b/src/newgrf_object.h
@@ -126,7 +126,7 @@ struct ObjectScopeResolver : public ScopeResolver {
 	}
 
 	uint32_t GetRandomBits() const override;
-	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const override;
+	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const override;
 };
 
 /** A resolver object to be used with feature 0F spritegroups. */
diff --git a/src/newgrf_railtype.cpp b/src/newgrf_railtype.cpp
index 25f6ea6c19..f6ca99148d 100644
--- a/src/newgrf_railtype.cpp
+++ b/src/newgrf_railtype.cpp
@@ -23,7 +23,7 @@
 	return GB(tmp, 0, 2);
 }
 
-/* virtual */ uint32_t RailTypeScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const
+/* virtual */ uint32_t RailTypeScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const
 {
 	if (this->tile == INVALID_TILE) {
 		switch (variable) {
@@ -55,7 +55,7 @@
 
 	Debug(grf, 1, "Unhandled rail type tile variable 0x{:X}", variable);
 
-	*available = false;
+	available = false;
 	return UINT_MAX;
 }
 
diff --git a/src/newgrf_railtype.h b/src/newgrf_railtype.h
index 3995409e9f..ca48a40c8d 100644
--- a/src/newgrf_railtype.h
+++ b/src/newgrf_railtype.h
@@ -32,7 +32,7 @@ struct RailTypeScopeResolver : public ScopeResolver {
 	}
 
 	uint32_t GetRandomBits() const override;
-	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const override;
+	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const override;
 };
 
 /** Resolver object for rail types. */
diff --git a/src/newgrf_roadstop.cpp b/src/newgrf_roadstop.cpp
index d8f6b196df..7e4e9be24a 100644
--- a/src/newgrf_roadstop.cpp
+++ b/src/newgrf_roadstop.cpp
@@ -64,7 +64,7 @@ uint32_t RoadStopScopeResolver::GetTriggers() const
 	return this->st == nullptr ? 0 : this->st->waiting_triggers;
 }
 
-uint32_t RoadStopScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const
+uint32_t RoadStopScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const
 {
 	auto get_road_type_variable = [&](RoadTramType rtt) -> uint32_t {
 		RoadType rt;
@@ -196,7 +196,7 @@ uint32_t RoadStopScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] u
 
 	if (this->st != nullptr) return this->st->GetNewGRFVariable(this->ro, variable, parameter, available);
 
-	*available = false;
+	available = false;
 	return UINT_MAX;
 }
 
diff --git a/src/newgrf_roadstop.h b/src/newgrf_roadstop.h
index 89111b5c62..e0b1a38ab6 100644
--- a/src/newgrf_roadstop.h
+++ b/src/newgrf_roadstop.h
@@ -92,7 +92,7 @@ struct RoadStopScopeResolver : public ScopeResolver {
 	uint32_t GetRandomBits() const override;
 	uint32_t GetTriggers() const override;
 
-	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const override;
+	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const override;
 };
 
 /** Road stop resolver. */
diff --git a/src/newgrf_roadtype.cpp b/src/newgrf_roadtype.cpp
index eeae364e0b..11aaa8ffde 100644
--- a/src/newgrf_roadtype.cpp
+++ b/src/newgrf_roadtype.cpp
@@ -23,7 +23,7 @@
 	return GB(tmp, 0, 2);
 }
 
-/* virtual */ uint32_t RoadTypeScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const
+/* virtual */ uint32_t RoadTypeScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const
 {
 	if (this->tile == INVALID_TILE) {
 		switch (variable) {
@@ -55,7 +55,7 @@
 
 	Debug(grf, 1, "Unhandled road type tile variable 0x{:X}", variable);
 
-	*available = false;
+	available = false;
 	return UINT_MAX;
 }
 
diff --git a/src/newgrf_roadtype.h b/src/newgrf_roadtype.h
index 40d5166c56..9f0566837a 100644
--- a/src/newgrf_roadtype.h
+++ b/src/newgrf_roadtype.h
@@ -33,7 +33,7 @@ struct RoadTypeScopeResolver : public ScopeResolver {
 	}
 
 	uint32_t GetRandomBits() const override;
-	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const override;
+	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const override;
 };
 
 /** Resolver object for road types. */
diff --git a/src/newgrf_spritegroup.cpp b/src/newgrf_spritegroup.cpp
index 4dc4f72c45..95d10d6308 100644
--- a/src/newgrf_spritegroup.cpp
+++ b/src/newgrf_spritegroup.cpp
@@ -53,7 +53,7 @@ TemporaryStorageArray<int32_t, 0x110> _temp_store;
 	}
 }
 
-static inline uint32_t GetVariable(const ResolverObject &object, ScopeResolver *scope, uint8_t variable, uint32_t parameter, bool *available)
+static inline uint32_t GetVariable(const ResolverObject &object, ScopeResolver *scope, uint8_t variable, uint32_t parameter, bool &available)
 {
 	uint32_t value;
 	switch (variable) {
@@ -103,10 +103,10 @@ static inline uint32_t GetVariable(const ResolverObject &object, ScopeResolver *
  * @param[out] available Set to false, in case the variable does not exist.
  * @return Value
  */
-/* virtual */ uint32_t ScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const
+/* virtual */ uint32_t ScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const
 {
 	Debug(grf, 1, "Unhandled scope variable 0x{:X}", variable);
-	*available = false;
+	available = false;
 	return UINT_MAX;
 }
 
@@ -205,9 +205,9 @@ const SpriteGroup *DeterministicSpriteGroup::Resolve(ResolverObject &object) con
 
 			/* Note: 'last_value' and 'reseed' are shared between the main chain and the procedure */
 		} else if (adjust.variable == 0x7B) {
-			value = GetVariable(object, scope, adjust.parameter, last_value, &available);
+			value = GetVariable(object, scope, adjust.parameter, last_value, available);
 		} else {
-			value = GetVariable(object, scope, adjust.variable, adjust.parameter, &available);
+			value = GetVariable(object, scope, adjust.variable, adjust.parameter, available);
 		}
 
 		if (!available) {
diff --git a/src/newgrf_spritegroup.h b/src/newgrf_spritegroup.h
index 7ca6d01ec0..cda6f4b3a3 100644
--- a/src/newgrf_spritegroup.h
+++ b/src/newgrf_spritegroup.h
@@ -294,7 +294,7 @@ struct ScopeResolver {
 	virtual uint32_t GetRandomBits() const;
 	virtual uint32_t GetTriggers() const;
 
-	virtual uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const;
+	virtual uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const;
 	virtual void StorePSA(uint reg, int32_t value);
 };
 
diff --git a/src/newgrf_station.cpp b/src/newgrf_station.cpp
index a53983e56c..af67fbf648 100644
--- a/src/newgrf_station.cpp
+++ b/src/newgrf_station.cpp
@@ -267,7 +267,7 @@ TownScopeResolver *StationResolverObject::GetTown()
 	return &*this->town_scope;
 }
 
-/* virtual */ uint32_t StationScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const
+/* virtual */ uint32_t StationScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const
 {
 	if (this->st == nullptr) {
 		/* Station does not exist, so we're in a purchase list or the land slope check callback. */
@@ -295,7 +295,7 @@ TownScopeResolver *StationResolverObject::GetTown()
 			case 0xFA: return ClampTo<uint16_t>(TimerGameCalendar::date - CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR); // Build date, clamped to a 16 bit value
 		}
 
-		*available = false;
+		available = false;
 		return UINT_MAX;
 	}
 
@@ -404,7 +404,7 @@ TownScopeResolver *StationResolverObject::GetTown()
 	return this->st->GetNewGRFVariable(this->ro, variable, parameter, available);
 }
 
-uint32_t Station::GetNewGRFVariable(const ResolverObject &object, uint8_t variable, uint8_t parameter, bool *available) const
+uint32_t Station::GetNewGRFVariable(const ResolverObject &object, uint8_t variable, uint8_t parameter, bool &available) const
 {
 	switch (variable) {
 		case 0x48: { // Accepted cargo types
@@ -466,11 +466,11 @@ uint32_t Station::GetNewGRFVariable(const ResolverObject &object, uint8_t variab
 
 	Debug(grf, 1, "Unhandled station variable 0x{:X}", variable);
 
-	*available = false;
+	available = false;
 	return UINT_MAX;
 }
 
-uint32_t Waypoint::GetNewGRFVariable(const ResolverObject &, uint8_t variable, [[maybe_unused]] uint8_t parameter, bool *available) const
+uint32_t Waypoint::GetNewGRFVariable(const ResolverObject &, uint8_t variable, [[maybe_unused]] uint8_t parameter, bool &available) const
 {
 	switch (variable) {
 		case 0x48: return 0; // Accepted cargo types
@@ -498,7 +498,7 @@ uint32_t Waypoint::GetNewGRFVariable(const ResolverObject &, uint8_t variable, [
 
 	Debug(grf, 1, "Unhandled station variable 0x{:X}", variable);
 
-	*available = false;
+	available = false;
 	return UINT_MAX;
 }
 
diff --git a/src/newgrf_station.h b/src/newgrf_station.h
index 225fd0fd51..5c244a270e 100644
--- a/src/newgrf_station.h
+++ b/src/newgrf_station.h
@@ -43,7 +43,7 @@ struct StationScopeResolver : public ScopeResolver {
 	uint32_t GetRandomBits() const override;
 	uint32_t GetTriggers() const override;
 
-	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const override;
+	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const override;
 };
 
 /** Station resolver. */
diff --git a/src/newgrf_town.cpp b/src/newgrf_town.cpp
index fb4f2e1ae1..d144d56561 100644
--- a/src/newgrf_town.cpp
+++ b/src/newgrf_town.cpp
@@ -15,10 +15,10 @@
 
 #include "safeguards.h"
 
-/* virtual */ uint32_t TownScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const
+/* virtual */ uint32_t TownScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const
 {
 	if (this->t == nullptr) {
-		*available = false;
+		available = false;
 		return UINT_MAX;
 	}
 
@@ -119,7 +119,7 @@
 
 	Debug(grf, 1, "Unhandled town variable 0x{:X}", variable);
 
-	*available = false;
+	available = false;
 	return UINT_MAX;
 }
 
diff --git a/src/newgrf_town.h b/src/newgrf_town.h
index 7c9bc3729e..b8bdb1f061 100644
--- a/src/newgrf_town.h
+++ b/src/newgrf_town.h
@@ -34,7 +34,7 @@ struct TownScopeResolver : public ScopeResolver {
 	{
 	}
 
-	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool *available) const override;
+	uint32_t GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const override;
 	void StorePSA(uint reg, int32_t value) override;
 };
 
diff --git a/src/station_base.h b/src/station_base.h
index 5b73de95ef..155e2fe420 100644
--- a/src/station_base.h
+++ b/src/station_base.h
@@ -516,7 +516,7 @@ public:
 		return IsAirportTile(tile) && GetStationIndex(tile) == this->index;
 	}
 
-	uint32_t GetNewGRFVariable(const ResolverObject &object, uint8_t variable, uint8_t parameter, bool *available) const override;
+	uint32_t GetNewGRFVariable(const ResolverObject &object, uint8_t variable, uint8_t parameter, bool &available) const override;
 
 	void GetTileArea(TileArea *ta, StationType type) const override;
 };
diff --git a/src/table/newgrf_debug_data.h b/src/table/newgrf_debug_data.h
index 836cec3445..1be431a939 100644
--- a/src/table/newgrf_debug_data.h
+++ b/src/table/newgrf_debug_data.h
@@ -78,7 +78,7 @@ class NIHVehicle : public NIHelper {
 	void SetStringParameters(uint index) const override  { this->SetSimpleStringParameters(STR_VEHICLE_NAME, index); }
 	uint32_t GetGRFID(uint index) const override                   { return Vehicle::Get(index)->GetGRFID(); }
 
-	uint Resolve(uint index, uint var, uint param, bool *avail) const override
+	uint Resolve(uint index, uint var, uint param, bool &avail) const override
 	{
 		Vehicle *v = Vehicle::Get(index);
 		VehicleResolverObject ro(v->engine_type, v, VehicleResolverObject::WO_CACHED);
@@ -143,7 +143,7 @@ class NIHStation : public NIHelper {
 	void SetStringParameters(uint index) const override  { this->SetObjectAtStringParameters(STR_STATION_NAME, GetStationIndex(index), index); }
 	uint32_t GetGRFID(uint index) const override           { return (this->IsInspectable(index)) ? GetStationSpec(index)->grf_prop.grffile->grfid : 0; }
 
-	uint Resolve(uint index, uint var, uint param, bool *avail) const override
+	uint Resolve(uint index, uint var, uint param, bool &avail) const override
 	{
 		StationResolverObject ro(GetStationSpec(index), Station::GetByTile(index), index);
 		return ro.GetScope(VSG_SCOPE_SELF)->GetVariable(var, param, avail);
@@ -208,7 +208,7 @@ class NIHHouse : public NIHelper {
 	void SetStringParameters(uint index) const override  { this->SetObjectAtStringParameters(STR_TOWN_NAME, GetTownIndex(index), index); }
 	uint32_t GetGRFID(uint index) const override           { return (this->IsInspectable(index)) ? HouseSpec::Get(GetHouseType(index))->grf_prop.grffile->grfid : 0; }
 
-	uint Resolve(uint index, uint var, uint param, bool *avail) const override
+	uint Resolve(uint index, uint var, uint param, bool &avail) const override
 	{
 		HouseResolverObject ro(GetHouseType(index), index, Town::GetByTile(index));
 		return ro.GetScope(VSG_SCOPE_SELF)->GetVariable(var, param, avail);
@@ -258,7 +258,7 @@ class NIHIndustryTile : public NIHelper {
 	void SetStringParameters(uint index) const override  { this->SetObjectAtStringParameters(STR_INDUSTRY_NAME, GetIndustryIndex(index), index); }
 	uint32_t GetGRFID(uint index) const override           { return (this->IsInspectable(index)) ? GetIndustryTileSpec(GetIndustryGfx(index))->grf_prop.grffile->grfid : 0; }
 
-	uint Resolve(uint index, uint var, uint param, bool *avail) const override
+	uint Resolve(uint index, uint var, uint param, bool &avail) const override
 	{
 		IndustryTileResolverObject ro(GetIndustryGfx(index), index, Industry::GetByTile(index));
 		return ro.GetScope(VSG_SCOPE_SELF)->GetVariable(var, param, avail);
@@ -371,7 +371,7 @@ class NIHIndustry : public NIHelper {
 	void SetStringParameters(uint index) const override  { this->SetSimpleStringParameters(STR_INDUSTRY_NAME, index); }
 	uint32_t GetGRFID(uint index) const override           { return (this->IsInspectable(index)) ? GetIndustrySpec(Industry::Get(index)->type)->grf_prop.grffile->grfid : 0; }
 
-	uint Resolve(uint index, uint var, uint param, bool *avail) const override
+	uint Resolve(uint index, uint var, uint param, bool &avail) const override
 	{
 		Industry *i = Industry::Get(index);
 		IndustriesResolverObject ro(i->location.tile, i, i->type);
@@ -434,7 +434,7 @@ class NIHObject : public NIHelper {
 	void SetStringParameters(uint index) const override  { this->SetObjectAtStringParameters(STR_NEWGRF_INSPECT_CAPTION_OBJECT_AT_OBJECT, INVALID_STRING_ID, index); }
 	uint32_t GetGRFID(uint index) const override           { return (this->IsInspectable(index)) ? ObjectSpec::GetByTile(index)->grf_prop.grffile->grfid : 0; }
 
-	uint Resolve(uint index, uint var, uint param, bool *avail) const override
+	uint Resolve(uint index, uint var, uint param, bool &avail) const override
 	{
 		ObjectResolverObject ro(ObjectSpec::GetByTile(index), Object::GetByTile(index), index);
 		return ro.GetScope(VSG_SCOPE_SELF)->GetVariable(var, param, avail);
@@ -468,7 +468,7 @@ class NIHRailType : public NIHelper {
 	void SetStringParameters(uint index) const override  { this->SetObjectAtStringParameters(STR_NEWGRF_INSPECT_CAPTION_OBJECT_AT_RAIL_TYPE, INVALID_STRING_ID, index); }
 	uint32_t GetGRFID(uint) const override               { return 0; }
 
-	uint Resolve(uint index, uint var, uint param, bool *avail) const override
+	uint Resolve(uint index, uint var, uint param, bool &avail) const override
 	{
 		/* There is no unique GRFFile for the tile. Multiple GRFs can define different parts of the railtype.
 		 * However, currently the NewGRF Debug GUI does not display variables depending on the GRF (like 0x7F) anyway. */
@@ -504,7 +504,7 @@ class NIHAirportTile : public NIHelper {
 	void SetStringParameters(uint index) const override  { this->SetObjectAtStringParameters(STR_STATION_NAME, GetStationIndex(index), index); }
 	uint32_t GetGRFID(uint index) const override           { return (this->IsInspectable(index)) ? AirportTileSpec::Get(GetAirportGfx(index))->grf_prop.grffile->grfid : 0; }
 
-	uint Resolve(uint index, uint var, uint param, bool *avail) const override
+	uint Resolve(uint index, uint var, uint param, bool &avail) const override
 	{
 		AirportTileResolverObject ro(AirportTileSpec::GetByTile(index), index, Station::GetByTile(index));
 		return ro.GetScope(VSG_SCOPE_SELF)->GetVariable(var, param, avail);
@@ -545,7 +545,7 @@ class NIHAirport : public NIHelper {
 	void SetStringParameters(uint index) const override  { this->SetObjectAtStringParameters(STR_STATION_NAME, index, Station::Get(index)->airport.tile); }
 	uint32_t GetGRFID(uint index) const override         { return (this->IsInspectable(index)) ? AirportSpec::Get(Station::Get(index)->airport.type)->grf_prop.grffile->grfid : 0; }
 
-	uint Resolve(uint index, uint var, uint param, bool *avail) const override
+	uint Resolve(uint index, uint var, uint param, bool &avail) const override
 	{
 		Station *st = Station::Get(index);
 		AirportResolverObject ro(st->airport.tile, st, st->airport.type, st->airport.layout);
@@ -592,7 +592,7 @@ class NIHTown : public NIHelper {
 	uint32_t GetGRFID(uint) const override               { return 0; }
 	bool PSAWithParameter() const override               { return true; }
 
-	uint Resolve(uint index, uint var, uint param, bool *avail) const override
+	uint Resolve(uint index, uint var, uint param, bool &avail) const override
 	{
 		TownResolverObject ro(nullptr, Town::Get(index), true);
 		return ro.GetScope(VSG_SCOPE_SELF)->GetVariable(var, param, avail);
@@ -636,7 +636,7 @@ class NIHRoadType : public NIHelper {
 	void SetStringParameters(uint index) const override  { this->SetObjectAtStringParameters(STR_NEWGRF_INSPECT_CAPTION_OBJECT_AT_ROAD_TYPE, INVALID_STRING_ID, index); }
 	uint32_t GetGRFID(uint) const override               { return 0; }
 
-	uint Resolve(uint index, uint var, uint param, bool *avail) const override
+	uint Resolve(uint index, uint var, uint param, bool &avail) const override
 	{
 		/* There is no unique GRFFile for the tile. Multiple GRFs can define different parts of the railtype.
 		 * However, currently the NewGRF Debug GUI does not display variables depending on the GRF (like 0x7F) anyway. */
@@ -702,7 +702,7 @@ class NIHRoadStop : public NIHelper {
 	void SetStringParameters(uint index) const override  { this->SetObjectAtStringParameters(STR_STATION_NAME, GetStationIndex(index), index); }
 	uint32_t GetGRFID(uint index) const override           { return (this->IsInspectable(index)) ? GetRoadStopSpec(index)->grf_prop.grffile->grfid : 0; }
 
-	uint Resolve(uint index, uint var, uint32_t param, bool *avail) const override
+	uint Resolve(uint index, uint var, uint32_t param, bool &avail) const override
 	{
 		int view = GetRoadStopDir(index);
 		if (IsDriveThroughStopTile(index)) view += 4;
diff --git a/src/waypoint_base.h b/src/waypoint_base.h
index f431958e6e..5e13f6e134 100644
--- a/src/waypoint_base.h
+++ b/src/waypoint_base.h
@@ -32,7 +32,7 @@ struct Waypoint final : SpecializedStation<Waypoint, true> {
 		return IsRailWaypointTile(tile) && GetStationIndex(tile) == this->index;
 	}
 
-	uint32_t GetNewGRFVariable(const struct ResolverObject &object, uint8_t variable, uint8_t parameter, bool *available) const override;
+	uint32_t GetNewGRFVariable(const struct ResolverObject &object, uint8_t variable, uint8_t parameter, bool &available) const override;
 
 	void GetTileArea(TileArea *ta, StationType type) const override;