diff --git a/src/newgrf_house.cpp b/src/newgrf_house.cpp
--- a/src/newgrf_house.cpp
+++ b/src/newgrf_house.cpp
@@ -25,7 +25,7 @@
 #include "safeguards.h"
 
 static BuildingCounts<uint32_t> _building_counts;
-static HouseClassMapping _class_mapping[HOUSE_CLASS_MAX];
+static std::array<HouseClassMapping, HOUSE_CLASS_MAX> _class_mapping;
 
 HouseOverrideManager _house_mngr(NEW_HOUSE_OFFSET, NUM_HOUSES, INVALID_HOUSE_ID);
 
@@ -72,6 +72,11 @@ uint32_t HouseResolverObject::GetDebugID
 	return HouseSpec::Get(this->house_scope.house_id)->grf_prop.local_id;
 }
 
+void ResetHouseClassIDs()
+{
+	_class_mapping = {};
+}
+
 HouseClassID AllocateHouseClassID(byte grf_class_id, uint32_t grfid)
 {
 	/* Start from 1 because 0 means that no class has been assigned. */
diff --git a/src/newgrf_house.h b/src/newgrf_house.h
--- a/src/newgrf_house.h
+++ b/src/newgrf_house.h
@@ -87,6 +87,7 @@ struct HouseClassMapping {
 	uint8_t  class_id;  ///< The class id within the grf file
 };
 
+void ResetHouseClassIDs();
 HouseClassID AllocateHouseClassID(byte grf_class_id, uint32_t grfid);
 
 void InitializeBuildingCounts();
diff --git a/src/town_cmd.cpp b/src/town_cmd.cpp
--- a/src/town_cmd.cpp
+++ b/src/town_cmd.cpp
@@ -3842,6 +3842,8 @@ HouseSpec _house_specs[NUM_HOUSES];
 
 void ResetHouses()
 {
+	ResetHouseClassIDs();
+
 	auto insert = std::copy(std::begin(_original_house_specs), std::end(_original_house_specs), std::begin(_house_specs));
 	std::fill(insert, std::end(_house_specs), HouseSpec{});