diff --git a/src/error.h b/src/error.h
index 0f1964fb80..f9480745f4 100644
--- a/src/error.h
+++ b/src/error.h
@@ -31,7 +31,7 @@ enum WarningLevel {
 class ErrorMessageData {
 protected:
 	bool is_critical;               ///< Whether the error message is critical.
-	std::vector<StringParameterBackup> params; ///< Backup of parameters of the message strings.
+	std::vector<StringParameterData> params; ///< Backup of parameters of the message strings.
 	const GRFFile *textref_stack_grffile; ///< NewGRF that filled the #TextRefStack for the error message.
 	uint textref_stack_size;        ///< Number of uint32_t values to put on the #TextRefStack for the error message.
 	uint32_t textref_stack[16];       ///< Values to put on the #TextRefStack for the error message.
diff --git a/src/lang/latvian.txt b/src/lang/latvian.txt
index 86e55c6c90..e2761fda4e 100644
--- a/src/lang/latvian.txt
+++ b/src/lang/latvian.txt
@@ -621,8 +621,8 @@ STR_GRAPH_CARGO_PAYMENT_RATES_CAPTION                           :{WHITE}Kravas a
 STR_GRAPH_CARGO_PAYMENT_RATES_DAYS                              :{TINY_FONT}{BLACK}Dienas ceļā
 STR_GRAPH_CARGO_PAYMENT_RATES_SECONDS                           :{TINY_FONT}{BLACK}Sekundes tranzītā
 STR_GRAPH_CARGO_PAYMENT_RATES_TITLE                             :{TINY_FONT}{BLACK}Izmaksas par 10 vienību (vai 10,000 litru) kravas pārvadāšanu par 20 lauciņiem
-STR_GRAPH_CARGO_ENABLE_ALL                                      :{TINY_FONT}{BLACK}Iespējot visu
-STR_GRAPH_CARGO_DISABLE_ALL                                     :{TINY_FONT}{BLACK}Atspējot visu
+STR_GRAPH_CARGO_ENABLE_ALL                                      :{TINY_FONT}{BLACK}Viss
+STR_GRAPH_CARGO_DISABLE_ALL                                     :{TINY_FONT}{BLACK}Nav
 STR_GRAPH_CARGO_TOOLTIP_ENABLE_ALL                              :{BLACK}Rādīt visas kravas samaksu salīdzināšanas diagrammā
 STR_GRAPH_CARGO_TOOLTIP_DISABLE_ALL                             :{BLACK}Nerādīt nevienu kravu samaksu salīdzināšanas diagrammā
 STR_GRAPH_CARGO_PAYMENT_TOGGLE_CARGO                            :{BLACK}Paslēgt kravas veida diagrammu
@@ -801,8 +801,8 @@ STR_SMALLMAP_INDUSTRY                                           :{TINY_FONT}{STR
 STR_SMALLMAP_LINKSTATS                                          :{TINY_FONT}{STRING}
 STR_SMALLMAP_COMPANY                                            :{TINY_FONT}{COMPANY}
 STR_SMALLMAP_TOWN                                               :{TINY_FONT}{WHITE}{TOWN}
-STR_SMALLMAP_DISABLE_ALL                                        :{BLACK}Atspējot visu
-STR_SMALLMAP_ENABLE_ALL                                         :{BLACK}Iespējot visu
+STR_SMALLMAP_DISABLE_ALL                                        :{BLACK}Neviena
+STR_SMALLMAP_ENABLE_ALL                                         :{BLACK}Viss
 STR_SMALLMAP_SHOW_HEIGHT                                        :{BLACK}Rādīt augstumu
 STR_SMALLMAP_SHOW_INDUSTRY_NAMES                                :{BLACK}Rādīt ražotņu nosaukumus
 STR_SMALLMAP_TOOLTIP_DISABLE_ALL_INDUSTRIES                     :{BLACK}Nerādīt uz kartes ražotnes
@@ -3905,6 +3905,7 @@ STR_COMPANY_VIEW_CAPTION                                        :{WHITE}{COMPANY
 STR_COMPANY_VIEW_PRESIDENT_MANAGER_TITLE                        :{WHITE}{PRESIDENT_NAME}{}{GOLD}(vadītājs)
 
 STR_COMPANY_VIEW_INAUGURATED_TITLE                              :{GOLD}Dibināts: {WHITE}{NUM}
+STR_COMPANY_VIEW_INAUGURATED_TITLE_WALLCLOCK                    :{GOLD}Inaugurācija: {WHITE}{NUM} ({NUM}. period)
 STR_COMPANY_VIEW_COLOUR_SCHEME_TITLE                            :{GOLD}Identitātes krāsu shēma
 STR_COMPANY_VIEW_VEHICLES_TITLE                                 :{GOLD}Transportlīdzekļi:
 STR_COMPANY_VIEW_TRAINS                                         :{WHITE}{COMMA} vilcien{P s i u}
diff --git a/src/lang/portuguese.txt b/src/lang/portuguese.txt
index 5372833f0c..887e3169c9 100644
--- a/src/lang/portuguese.txt
+++ b/src/lang/portuguese.txt
@@ -620,8 +620,8 @@ STR_GRAPH_CARGO_PAYMENT_RATES_CAPTION                           :{WHITE}Tarifas
 STR_GRAPH_CARGO_PAYMENT_RATES_DAYS                              :{TINY_FONT}{BLACK}Dias em trânsito
 STR_GRAPH_CARGO_PAYMENT_RATES_SECONDS                           :{TINY_FONT}{BLACK}Segundos em trânsito
 STR_GRAPH_CARGO_PAYMENT_RATES_TITLE                             :{TINY_FONT}{BLACK}Pagamento por entregar 10 unidades (ou 10 000 litros) de carga numa distância de 20 quadrados
-STR_GRAPH_CARGO_ENABLE_ALL                                      :{TINY_FONT}{BLACK}Ativar tudo
-STR_GRAPH_CARGO_DISABLE_ALL                                     :{TINY_FONT}{BLACK}Desativar tudo
+STR_GRAPH_CARGO_ENABLE_ALL                                      :{TINY_FONT}{BLACK}Tudo
+STR_GRAPH_CARGO_DISABLE_ALL                                     :{TINY_FONT}{BLACK}Nenhum
 STR_GRAPH_CARGO_TOOLTIP_ENABLE_ALL                              :{BLACK}Mostrar todas as cargas no gráfico de tarifas por carga
 STR_GRAPH_CARGO_TOOLTIP_DISABLE_ALL                             :{BLACK}Não mostrar carga no gráfico de tarifas por carga
 STR_GRAPH_CARGO_PAYMENT_TOGGLE_CARGO                            :{BLACK}Alternar o gráfico para este tipo de carga
@@ -800,8 +800,8 @@ STR_SMALLMAP_INDUSTRY                                           :{TINY_FONT}{STR
 STR_SMALLMAP_LINKSTATS                                          :{TINY_FONT}{STRING}
 STR_SMALLMAP_COMPANY                                            :{TINY_FONT}{COMPANY}
 STR_SMALLMAP_TOWN                                               :{TINY_FONT}{WHITE}{TOWN}
-STR_SMALLMAP_DISABLE_ALL                                        :{BLACK}Desativar tudo
-STR_SMALLMAP_ENABLE_ALL                                         :{BLACK}Ativar tudo
+STR_SMALLMAP_DISABLE_ALL                                        :{BLACK}Nenhum
+STR_SMALLMAP_ENABLE_ALL                                         :{BLACK}Tudo
 STR_SMALLMAP_SHOW_HEIGHT                                        :{BLACK}Mostrar altura
 STR_SMALLMAP_SHOW_INDUSTRY_NAMES                                :{BLACK}Mostrar nomes das indústrias
 STR_SMALLMAP_TOOLTIP_DISABLE_ALL_INDUSTRIES                     :{BLACK}Não mostrar indústrias no mapa
diff --git a/src/misc_gui.cpp b/src/misc_gui.cpp
index cb97d7c8c3..f77caa42e0 100644
--- a/src/misc_gui.cpp
+++ b/src/misc_gui.cpp
@@ -668,7 +668,7 @@ static WindowDesc _tool_tips_desc(
 struct TooltipsWindow : public Window
 {
 	StringID string_id;               ///< String to display as tooltip.
-	std::vector<StringParameterBackup> params; ///< The string parameters.
+	std::vector<StringParameterData> params; ///< The string parameters.
 	TooltipCloseCondition close_cond; ///< Condition for closing the window.
 
 	TooltipsWindow(Window *parent, StringID str, uint paramcount, TooltipCloseCondition close_tooltip) : Window(_tool_tips_desc)
@@ -1089,7 +1089,7 @@ void ShowQueryString(StringID str, StringID caption, uint maxsize, Window *paren
  */
 struct QueryWindow : public Window {
 	QueryCallbackProc *proc; ///< callback function executed on closing of popup. Window* points to parent, bool is true if 'yes' clicked, false otherwise
-	std::vector<StringParameterBackup> params; ///< local copy of #_global_string_params
+	std::vector<StringParameterData> params; ///< local copy of #_global_string_params
 	StringID message;        ///< message shown for query window
 
 	QueryWindow(WindowDesc &desc, StringID caption, StringID message, Window *parent, QueryCallbackProc *callback) : Window(desc)
diff --git a/src/newgrf_station.cpp b/src/newgrf_station.cpp
index bef7e61c5a..8a307b2640 100644
--- a/src/newgrf_station.cpp
+++ b/src/newgrf_station.cpp
@@ -125,7 +125,7 @@ uint32_t GetPlatformInfo(Axis axis, uint8_t tile, int platforms, int length, int
 	}
 	SB(retval, 16, 4, std::min(15, length));
 	SB(retval, 20, 4, std::min(15, platforms));
-	SB(retval, 24, 4, tile);
+	SB(retval, 24, 8, tile);
 
 	return retval;
 }
diff --git a/src/news_gui.cpp b/src/news_gui.cpp
index c5aedecbf6..3ba464b0e5 100644
--- a/src/news_gui.cpp
+++ b/src/news_gui.cpp
@@ -296,7 +296,7 @@ struct NewsWindow : Window {
 		this->CreateNestedTree();
 
 		/* For company news with a face we have a separate headline in param[0] */
-		if (&desc == &_company_news_desc) this->GetWidget<NWidgetCore>(WID_N_TITLE)->widget_data = this->ni->params[0].data;
+		if (&desc == &_company_news_desc) this->GetWidget<NWidgetCore>(WID_N_TITLE)->widget_data = std::get<uint64_t>(this->ni->params[0]);
 
 		NWidgetCore *nwid = this->GetWidget<NWidgetCore>(WID_N_SHOW_GROUP);
 		if (ni->reftype1 == NR_VEHICLE && nwid != nullptr) {
@@ -603,7 +603,7 @@ private:
 	{
 		/* Company news with a face have a separate headline, so the normal message is shifted by two params */
 		CopyInDParam(std::span(this->ni->params.data() + 2, this->ni->params.size() - 2));
-		return this->ni->params[1].data;
+		return std::get<uint64_t>(this->ni->params[1]);
 	}
 
 	StringID GetNewVehicleMessageString(WidgetID widget) const
@@ -986,7 +986,7 @@ void ChangeVehicleNews(VehicleID from_index, VehicleID to_index)
 	for (auto &ni : _news) {
 		if (ni.reftype1 == NR_VEHICLE && ni.ref1 == from_index) ni.ref1 = to_index;
 		if (ni.reftype2 == NR_VEHICLE && ni.ref2 == from_index) ni.ref2 = to_index;
-		if (ni.flags & NF_VEHICLE_PARAM0 && ni.params[0].data == from_index) ni.params[0] = to_index;
+		if (ni.flags & NF_VEHICLE_PARAM0 && std::get<uint64_t>(ni.params[0]) == from_index) ni.params[0] = to_index;
 	}
 }
 
diff --git a/src/news_type.h b/src/news_type.h
index cbafbef1ce..a83402f382 100644
--- a/src/news_type.h
+++ b/src/news_type.h
@@ -139,7 +139,7 @@ struct NewsItem {
 
 	std::unique_ptr<const NewsAllocatedData> data; ///< Custom data for the news item that will be deallocated (deleted) when the news item has reached its end.
 
-	std::vector<StringParameterBackup> params; ///< Parameters for string resolving.
+	std::vector<StringParameterData> params; ///< Parameters for string resolving.
 
 	NewsItem(StringID string_id, NewsType type, NewsFlag flags, NewsReferenceType reftype1, uint32_t ref1, NewsReferenceType reftype2, uint32_t ref2, const NewsAllocatedData *data);
 };
diff --git a/src/saveload/company_sl.cpp b/src/saveload/company_sl.cpp
index 8e49af0eed..5abf18157b 100644
--- a/src/saveload/company_sl.cpp
+++ b/src/saveload/company_sl.cpp
@@ -441,6 +441,38 @@ public:
 	void LoadCheck(CompanyProperties *c) const override { this->Load(c); }
 };
 
+class SlAllowListData : public DefaultSaveLoadHandler<SlAllowListData, CompanyProperties> {
+public:
+	struct KeyWrapper {
+		std::string key;
+	};
+
+	inline static const SaveLoad description[] = {
+		SLE_SSTR(KeyWrapper, key, SLE_STR),
+	};
+	inline const static SaveLoadCompatTable compat_description = {};
+
+	void Save(CompanyProperties *cprops) const override
+	{
+		SlSetStructListLength(cprops->allow_list.size());
+		for (std::string &str : cprops->allow_list) {
+			SlObject(&str, this->GetDescription());
+		}
+	}
+
+	void Load(CompanyProperties *cprops) const override
+	{
+		size_t num_keys = SlGetStructListLength(UINT32_MAX);
+		cprops->allow_list.clear();
+		cprops->allow_list.resize(num_keys);
+		for (std::string &str : cprops->allow_list) {
+			SlObject(&str, this->GetLoadDescription());
+		}
+	}
+
+	void LoadCheck(CompanyProperties *cprops) const override { this->Load(cprops); }
+};
+
 /* Save/load of companies */
 static const SaveLoad _company_desc[] = {
 	    SLE_VAR(CompanyProperties, name_2,          SLE_UINT32),
@@ -451,7 +483,8 @@ static const SaveLoad _company_desc[] = {
 	    SLE_VAR(CompanyProperties, president_name_2, SLE_UINT32),
 	SLE_CONDSSTR(CompanyProperties, president_name,  SLE_STR | SLF_ALLOW_CONTROL, SLV_84, SL_MAX_VERSION),
 
-	SLE_CONDVECTOR(CompanyProperties, allow_list, SLE_STR, SLV_COMPANY_ALLOW_LIST, SL_MAX_VERSION),
+	SLE_CONDVECTOR(CompanyProperties, allow_list, SLE_STR, SLV_COMPANY_ALLOW_LIST, SLV_COMPANY_ALLOW_LIST_V2),
+	SLEG_CONDSTRUCTLIST("allow_list", SlAllowListData, SLV_COMPANY_ALLOW_LIST_V2, SL_MAX_VERSION),
 
 	    SLE_VAR(CompanyProperties, face,            SLE_UINT32),
 
diff --git a/src/saveload/saveload.cpp b/src/saveload/saveload.cpp
index 81852f7cf8..68019e8dab 100644
--- a/src/saveload/saveload.cpp
+++ b/src/saveload/saveload.cpp
@@ -1246,17 +1246,13 @@ public:
 	 */
 	static size_t SlCalcLen(const void *storage, VarType conv, SaveLoadType cmd = SL_VAR)
 	{
-		assert(cmd == SL_VAR || cmd == SL_REF || cmd == SL_STDSTR);
+		assert(cmd == SL_VAR || cmd == SL_REF);
 
 		const SlStorageT *list = static_cast<const SlStorageT *>(storage);
 
-		size_t type_size = SlGetArrayLength(list->size());
-		if constexpr (std::is_same_v<std::vector<std::string>, SlStorageT> || std::is_same_v<std::deque<std::string>, SlStorageT>) {
-			return std::accumulate(list->begin(), list->end(), type_size, [](size_t sum, const std::string &str) { return sum + SlCalcStdStringLen(&str); });
-		} else {
-			size_t item_size = SlCalcConvFileLen(cmd == SL_VAR ? conv : (VarType)SLE_FILE_U32);
-			return list->size() * item_size + type_size;
-		}
+		int type_size = SlGetArrayLength(list->size());
+		int item_size = SlCalcConvFileLen(cmd == SL_VAR ? conv : (VarType)SLE_FILE_U32);
+		return list->size() * item_size + type_size;
 	}
 
 	static void SlSaveLoadMember(SaveLoadType cmd, Tvar *item, VarType conv)
@@ -1368,7 +1364,12 @@ static inline size_t SlCalcDequeLen(const void *deque, VarType conv)
 		case SLE_VAR_U32: return SlStorageHelper<std::deque, uint32_t>::SlCalcLen(deque, conv);
 		case SLE_VAR_I64: return SlStorageHelper<std::deque, int64_t>::SlCalcLen(deque, conv);
 		case SLE_VAR_U64: return SlStorageHelper<std::deque, uint64_t>::SlCalcLen(deque, conv);
-		case SLE_VAR_STR: return SlStorageHelper<std::deque, std::string>::SlCalcLen(deque, conv, SL_STDSTR);
+
+		case SLE_VAR_STR:
+			/* Strings are a length-prefixed field type in the savegame table format,
+			 * these may not be directly stored in another length-prefixed container type. */
+			NOT_REACHED();
+
 		default: NOT_REACHED();
 	}
 }
@@ -1390,7 +1391,16 @@ static void SlDeque(void *deque, VarType conv)
 		case SLE_VAR_U32: SlStorageHelper<std::deque, uint32_t>::SlSaveLoad(deque, conv); break;
 		case SLE_VAR_I64: SlStorageHelper<std::deque, int64_t>::SlSaveLoad(deque, conv); break;
 		case SLE_VAR_U64: SlStorageHelper<std::deque, uint64_t>::SlSaveLoad(deque, conv); break;
-		case SLE_VAR_STR: SlStorageHelper<std::deque, std::string>::SlSaveLoad(deque, conv, SL_STDSTR); break;
+
+		case SLE_VAR_STR:
+			/* Strings are a length-prefixed field type in the savegame table format,
+			 * these may not be directly stored in another length-prefixed container type.
+			 * This is permitted for load-related actions, because invalid fields of this type are present
+			 * from SLV_COMPANY_ALLOW_LIST up to SLV_COMPANY_ALLOW_LIST_V2. */
+			assert(_sl.action != SLA_SAVE);
+			SlStorageHelper<std::deque, std::string>::SlSaveLoad(deque, conv, SL_STDSTR);
+			break;
+
 		default: NOT_REACHED();
 	}
 }
@@ -1412,7 +1422,12 @@ static inline size_t SlCalcVectorLen(const void *vector, VarType conv)
 		case SLE_VAR_U32: return SlStorageHelper<std::vector, uint32_t>::SlCalcLen(vector, conv);
 		case SLE_VAR_I64: return SlStorageHelper<std::vector, int64_t>::SlCalcLen(vector, conv);
 		case SLE_VAR_U64: return SlStorageHelper<std::vector, uint64_t>::SlCalcLen(vector, conv);
-		case SLE_VAR_STR: return SlStorageHelper<std::vector, std::string>::SlCalcLen(vector, conv, SL_STDSTR);
+
+		case SLE_VAR_STR:
+			/* Strings are a length-prefixed field type in the savegame table format,
+			 * these may not be directly stored in another length-prefixed container type. */
+			NOT_REACHED();
+
 		default: NOT_REACHED();
 	}
 }
@@ -1434,7 +1449,16 @@ static void SlVector(void *vector, VarType conv)
 		case SLE_VAR_U32: SlStorageHelper<std::vector, uint32_t>::SlSaveLoad(vector, conv); break;
 		case SLE_VAR_I64: SlStorageHelper<std::vector, int64_t>::SlSaveLoad(vector, conv); break;
 		case SLE_VAR_U64: SlStorageHelper<std::vector, uint64_t>::SlSaveLoad(vector, conv); break;
-		case SLE_VAR_STR: SlStorageHelper<std::vector, std::string>::SlSaveLoad(vector, conv, SL_STDSTR); break;
+
+		case SLE_VAR_STR:
+			/* Strings are a length-prefixed field type in the savegame table format,
+			 * these may not be directly stored in another length-prefixed container type.
+			 * This is permitted for load-related actions, because invalid fields of this type are present
+			 * from SLV_COMPANY_ALLOW_LIST up to SLV_COMPANY_ALLOW_LIST_V2. */
+			assert(_sl.action != SLA_SAVE);
+			SlStorageHelper<std::vector, std::string>::SlSaveLoad(vector, conv, SL_STDSTR);
+			break;
+
 		default: NOT_REACHED();
 	}
 }
diff --git a/src/saveload/saveload.h b/src/saveload/saveload.h
index 01cbbda828..d12fb00e02 100644
--- a/src/saveload/saveload.h
+++ b/src/saveload/saveload.h
@@ -386,6 +386,7 @@ enum SaveLoadVersion : uint16_t {
 	SLV_COMPANY_INAUGURATED_PERIOD,         ///< 339  PR#12798 Companies show the period inaugurated in wallclock mode.
 
 	SLV_ROAD_STOP_TILE_DATA,                ///< 340  PR#12883 Move storage of road stop tile data, also save for road waypoints.
+	SLV_COMPANY_ALLOW_LIST_V2,              ///< 341  PR#12908 Fixed savegame format for saving of list of client keys that are allowed to join this company.
 
 	SL_MAX_VERSION,                         ///< Highest possible saveload version
 };
diff --git a/src/strings.cpp b/src/strings.cpp
index ac959f7ddd..61aefacdca 100644
--- a/src/strings.cpp
+++ b/src/strings.cpp
@@ -76,9 +76,9 @@ void StringParameters::PrepareForNextRun()
  * Get the next parameter from our parameters.
  * This updates the offset, so the next time this is called the next parameter
  * will be read.
- * @return The pointer to the next parameter.
+ * @return The next parameter.
  */
-StringParameter *StringParameters::GetNextParameterPointer()
+const StringParameter &StringParameters::GetNextParameterReference()
 {
 	assert(this->next_type == 0 || (SCC_CONTROL_START <= this->next_type && this->next_type <= SCC_CONTROL_END));
 	if (this->offset >= this->parameters.size()) {
@@ -92,7 +92,7 @@ StringParameter *StringParameters::GetNextParameterPointer()
 	}
 	param.type = this->next_type;
 	this->next_type = 0;
-	return &param;
+	return param;
 }
 
 
@@ -113,7 +113,7 @@ void SetDParam(size_t n, uint64_t v)
  */
 uint64_t GetDParam(size_t n)
 {
-	return _global_string_params.GetParam(n);
+	return std::get<uint64_t>(_global_string_params.GetParam(n));
 }
 
 /**
@@ -156,15 +156,10 @@ void SetDParamMaxDigits(size_t n, uint count, FontSize size)
  * Copy the parameters from the backup into the global string parameter array.
  * @param backup The backup to copy from.
  */
-void CopyInDParam(const std::span<const StringParameterBackup> backup)
+void CopyInDParam(const std::span<const StringParameterData> backup)
 {
 	for (size_t i = 0; i < backup.size(); i++) {
-		auto &value = backup[i];
-		if (value.string.has_value()) {
-			_global_string_params.SetParam(i, value.string.value());
-		} else {
-			_global_string_params.SetParam(i, value.data);
-		}
+		_global_string_params.SetParam(i, backup[i]);
 	}
 }
 
@@ -173,16 +168,11 @@ void CopyInDParam(const std::span<const StringParameterBackup> backup)
  * @param backup The backup to write to.
  * @param num Number of string parameters to copy.
  */
-void CopyOutDParam(std::vector<StringParameterBackup> &backup, size_t num)
+void CopyOutDParam(std::vector<StringParameterData> &backup, size_t num)
 {
 	backup.resize(num);
 	for (size_t i = 0; i < backup.size(); i++) {
-		const char *str = _global_string_params.GetParamStr(i);
-		if (str != nullptr) {
-			backup[i] = str;
-		} else {
-			backup[i] = _global_string_params.GetParam(i);
-		}
+		backup[i] = _global_string_params.GetParam(i);
 	}
 }
 
@@ -191,20 +181,12 @@ void CopyOutDParam(std::vector<StringParameterBackup> &backup, size_t num)
  * @param backup The backup to check against.
  * @return True when the parameters have changed, otherwise false.
  */
-bool HaveDParamChanged(const std::vector<StringParameterBackup> &backup)
+bool HaveDParamChanged(const std::span<const StringParameterData> backup)
 {
-	bool changed = false;
-	for (size_t i = 0; !changed && i < backup.size(); i++) {
-		bool global_has_string = _global_string_params.GetParamStr(i) != nullptr;
-		if (global_has_string != backup[i].string.has_value()) return true;
-
-		if (global_has_string) {
-			changed = backup[i].string.value() != _global_string_params.GetParamStr(i);
-		} else {
-			changed = backup[i].data != _global_string_params.GetParam(i);
-		}
+	for (size_t i = 0; i < backup.size(); i++) {
+		if (backup[i] != _global_string_params.GetParam(i)) return true;
 	}
-	return changed;
+	return false;
 }
 
 static void StationGetSpecialString(StringBuilder &builder, StationFacility x);
@@ -271,14 +253,24 @@ void GetStringWithArgs(StringBuilder &builder, StringID string, StringParameters
 	switch (tab) {
 		case TEXT_TAB_TOWN:
 			if (index >= 0xC0 && !game_script) {
-				GetSpecialTownNameString(builder, index - 0xC0, args.GetNextParameter<uint32_t>());
+				try {
+					GetSpecialTownNameString(builder, index - 0xC0, args.GetNextParameter<uint32_t>());
+				} catch (const std::runtime_error &e) {
+					Debug(misc, 0, "GetStringWithArgs: {}", e.what());
+					builder += "(invalid string parameter)";
+				}
 				return;
 			}
 			break;
 
 		case TEXT_TAB_SPECIAL:
 			if (index >= 0xE4 && !game_script) {
-				GetSpecialNameString(builder, index - 0xE4, args);
+				try {
+					GetSpecialNameString(builder, index - 0xE4, args);
+				} catch (const std::runtime_error &e) {
+					Debug(misc, 0, "GetStringWithArgs: {}", e.what());
+					builder += "(invalid string parameter)";
+				}
 				return;
 			}
 			break;
@@ -1106,7 +1098,7 @@ static void FormatString(StringBuilder &builder, const char *str_arg, StringPara
 				case SCC_PLURAL_LIST: { // {P}
 					int plural_form = *str++;          // contains the plural form for this string
 					size_t offset = orig_offset + (uint8_t)*str++;
-					int64_t v = args.GetParam(offset); // contains the number that determines plural
+					int64_t v = std::get<uint64_t>(args.GetParam(offset)); // contains the number that determines plural
 					str = ParseStringChoice(str, DeterminePluralForm(v, plural_form), builder);
 					break;
 				}
diff --git a/src/strings_func.h b/src/strings_func.h
index 21a77705d8..3ee91a0af5 100644
--- a/src/strings_func.h
+++ b/src/strings_func.h
@@ -98,9 +98,9 @@ void SetDParamStr(size_t n, const char *str);
 void SetDParamStr(size_t n, const std::string &str);
 void SetDParamStr(size_t n, std::string &&str);
 
-void CopyInDParam(const std::span<const StringParameterBackup> backup);
-void CopyOutDParam(std::vector<StringParameterBackup> &backup, size_t num);
-bool HaveDParamChanged(const std::vector<StringParameterBackup> &backup);
+void CopyInDParam(const std::span<const StringParameterData> backup);
+void CopyOutDParam(std::vector<StringParameterData> &backup, size_t num);
+bool HaveDParamChanged(const std::span<const StringParameterData> backup);
 
 uint64_t GetDParam(size_t n);
 
diff --git a/src/strings_internal.h b/src/strings_internal.h
index 3095e33107..4d6b1a5b7e 100644
--- a/src/strings_internal.h
+++ b/src/strings_internal.h
@@ -15,8 +15,7 @@
 
 /** The data required to format and validate a single parameter of a string. */
 struct StringParameter {
-	uint64_t data; ///< The data of the parameter.
-	std::unique_ptr<std::string> string; ///< Copied string value, if it has any.
+	StringParameterData data; ///< The data of the parameter.
 	char32_t type; ///< The #StringControlCode to interpret this data with when it's the first parameter, otherwise '\0'.
 };
 
@@ -32,7 +31,7 @@ protected:
 		parameters(parameters)
 	{}
 
-	StringParameter *GetNextParameterPointer();
+	const StringParameter &GetNextParameterReference();
 
 public:
 	/**
@@ -92,8 +91,10 @@ public:
 	template <typename T>
 	T GetNextParameter()
 	{
-		auto ptr = GetNextParameterPointer();
-		return static_cast<T>(ptr->data);
+		const auto &param = GetNextParameterReference();
+		const uint64_t *data = std::get_if<uint64_t>(&param.data);
+		if (data != nullptr) return static_cast<T>(*data);
+		throw std::runtime_error("Attempt to read string parameter as integer");
 	}
 
 	/**
@@ -104,8 +105,10 @@ public:
 	 */
 	const char *GetNextParameterString()
 	{
-		auto ptr = GetNextParameterPointer();
-		return ptr->string != nullptr ? ptr->string->c_str() : nullptr;
+		const auto &param = GetNextParameterReference();
+		const std::string *data = std::get_if<std::string>(&param.data);
+		if (data != nullptr) return data->c_str();
+		throw std::runtime_error("Attempt to read integer parameter as string");
 	}
 
 	/**
@@ -146,11 +149,16 @@ public:
 		return this->parameters[offset].type;
 	}
 
+	void SetParam(size_t n, const StringParameterData &v)
+	{
+		assert(n < this->parameters.size());
+		this->parameters[n].data = v;
+	}
+
 	void SetParam(size_t n, uint64_t v)
 	{
 		assert(n < this->parameters.size());
 		this->parameters[n].data = v;
-		this->parameters[n].string.reset();
 	}
 
 	template <typename T, std::enable_if_t<std::is_base_of<StrongTypedefBase, T>::value, int> = 0>
@@ -162,8 +170,7 @@ public:
 	void SetParam(size_t n, const char *str)
 	{
 		assert(n < this->parameters.size());
-		this->parameters[n].data = 0;
-		this->parameters[n].string = std::make_unique<std::string>(str);
+		this->parameters[n].data = str;
 	}
 
 	void SetParam(size_t n, const std::string &str) { this->SetParam(n, str.c_str()); }
@@ -171,28 +178,14 @@ public:
 	void SetParam(size_t n, std::string &&str)
 	{
 		assert(n < this->parameters.size());
-		this->parameters[n].data = 0;
-		this->parameters[n].string = std::make_unique<std::string>(std::move(str));
+		this->parameters[n].data = std::move(str);
 	}
 
-	uint64_t GetParam(size_t n) const
+	const StringParameterData &GetParam(size_t n) const
 	{
 		assert(n < this->parameters.size());
-		assert(this->parameters[n].string == nullptr);
 		return this->parameters[n].data;
 	}
-
-	/**
-	 * Get the stored string of the parameter, or \c nullptr when there is none.
-	 * @param n The index into the parameters.
-	 * @return The stored string.
-	 */
-	const char *GetParamStr(size_t n) const
-	{
-		assert(n < this->parameters.size());
-		auto &param = this->parameters[n];
-		return param.string != nullptr ? param.string->c_str() : nullptr;
-	}
 };
 
 /**
diff --git a/src/strings_type.h b/src/strings_type.h
index 5e6d715b63..49a0965d59 100644
--- a/src/strings_type.h
+++ b/src/strings_type.h
@@ -88,34 +88,6 @@ enum SpecialStrings {
 	SPECSTR_PRESIDENT_NAME     = 0x70E7,
 };
 
-/** Data that is to be stored when backing up StringParameters. */
-struct StringParameterBackup {
-	uint64_t data; ///< The data field; valid *when* string has no value.
-	std::optional<std::string> string; ///< The string value.
-
-	/**
-	 * Assign the numeric data with the given value, while clearing the stored string.
-	 * @param data The new value of the data field.
-	 * @return This object.
-	 */
-	StringParameterBackup &operator=(uint64_t data)
-	{
-		this->string.reset();
-		this->data = data;
-		return *this;
-	}
-
-	/**
-	 * Assign a copy of the given string to the string field, while clearing the data field.
-	 * @param string The new value of the string.
-	 * @return This object.
-	 */
-	StringParameterBackup &operator=(const std::string_view string)
-	{
-		this->data = 0;
-		this->string.emplace(string);
-		return *this;
-	}
-};
+using StringParameterData = std::variant<uint64_t, std::string>;
 
 #endif /* STRINGS_TYPE_H */
diff --git a/src/tests/strings_func.cpp b/src/tests/strings_func.cpp
index dd70b0a365..f82cdd92be 100644
--- a/src/tests/strings_func.cpp
+++ b/src/tests/strings_func.cpp
@@ -18,7 +18,7 @@ TEST_CASE("HaveDParamChanged")
 	SetDParam(0, 0);
 	SetDParamStr(1, "some string");
 
-	std::vector<StringParameterBackup> backup;
+	std::vector<StringParameterData> backup;
 	CopyOutDParam(backup, 2);
 
 	CHECK(HaveDParamChanged(backup) == false);
diff --git a/src/texteff.cpp b/src/texteff.cpp
index 10b276232e..fbec86d04f 100644
--- a/src/texteff.cpp
+++ b/src/texteff.cpp
@@ -21,7 +21,7 @@
 
 /** Container for all information about a text effect */
 struct TextEffect : public ViewportSign {
-	std::vector<StringParameterBackup> params; ///< Backup of string parameters
+	std::vector<StringParameterData> params; ///< Backup of string parameters
 	StringID string_id;  ///< String to draw for the text effect, if INVALID_STRING_ID then it's not valid
 	uint8_t duration;      ///< How long the text effect should stay, in ticks (applies only when mode == TE_RISING)
 	TextEffectMode mode; ///< Type of text effect