diff --git a/src/settings_gui.cpp b/src/settings_gui.cpp
--- a/src/settings_gui.cpp
+++ b/src/settings_gui.cpp
@@ -17,6 +17,7 @@
 #include "town.h"
 #include "settings_internal.h"
 #include "newgrf_townname.h"
+#include "townname_type.h"
 #include "strings_func.h"
 #include "window_func.h"
 #include "string_func.h"
@@ -73,7 +74,6 @@ static const StringID _font_zoom_dropdow
 	INVALID_STRING_ID,
 };
 
-int _nb_orig_names = SPECSTR_TOWNNAME_LAST - SPECSTR_TOWNNAME_START + 1; ///< Number of original town names.
 static StringID *_grf_names = nullptr; ///< Pointer to town names defined by NewGRFs.
 static int _nb_grf_names = 0;       ///< Number of town names defined by NewGRFs.
 
@@ -97,8 +97,8 @@ void InitGRFTownGeneratorNames()
  */
 static inline StringID TownName(int town_name)
 {
-	if (town_name < _nb_orig_names) return STR_GAME_OPTIONS_TOWN_NAME_ORIGINAL_ENGLISH + town_name;
-	town_name -= _nb_orig_names;
+	if (town_name < BUILTIN_TOWNNAME_GENERATOR_COUNT) return STR_GAME_OPTIONS_TOWN_NAME_ORIGINAL_ENGLISH + town_name;
+	town_name -= BUILTIN_TOWNNAME_GENERATOR_COUNT;
 	if (town_name < _nb_grf_names) return _grf_names[town_name];
 	return STR_UNDEFINED;
 }
@@ -245,7 +245,7 @@ struct GameOptionsWindow : Window {
 
 				/* Add and sort newgrf townnames generators */
 				for (int i = 0; i < _nb_grf_names; i++) {
-					int result = _nb_orig_names + i;
+					int result = BUILTIN_TOWNNAME_GENERATOR_COUNT + i;
 					list.emplace_back(new DropDownListStringItem(_grf_names[i], result, enabled_item != result && enabled_item >= 0));
 				}
 				std::sort(list.begin(), list.end(), DropDownListStringItem::NatSortFunc);
@@ -258,7 +258,7 @@ struct GameOptionsWindow : Window {
 				}
 
 				/* Add and sort original townnames generators */
-				for (int i = 0; i < _nb_orig_names; i++) {
+				for (int i = 0; i < BUILTIN_TOWNNAME_GENERATOR_COUNT; i++) {
 					list.emplace_back(new DropDownListStringItem(STR_GAME_OPTIONS_TOWN_NAME_ORIGINAL_ENGLISH + i, i, enabled_item != i && enabled_item >= 0));
 				}
 				std::sort(list.begin() + newgrf_size, list.end(), DropDownListStringItem::NatSortFunc);
diff --git a/src/town_cmd.cpp b/src/town_cmd.cpp
--- a/src/town_cmd.cpp
+++ b/src/town_cmd.cpp
@@ -1841,15 +1841,10 @@ static void DoCreateTown(Town *t, TileIn
 	t->exclusive_counter = 0;
 	t->statues = 0;
 
-	extern int _nb_orig_names;
-	if (_settings_game.game_creation.town_name < _nb_orig_names) {
-		/* Original town name */
-		t->townnamegrfid = 0;
-		t->townnametype = SPECSTR_TOWNNAME_START + _settings_game.game_creation.town_name;
-	} else {
-		/* Newgrf town name */
-		t->townnamegrfid = GetGRFTownNameId(_settings_game.game_creation.town_name  - _nb_orig_names);
-		t->townnametype  = GetGRFTownNameType(_settings_game.game_creation.town_name - _nb_orig_names);
+	{
+		TownNameParams tnp(_settings_game.game_creation.town_name);
+		t->townnamegrfid = tnp.grfid;
+		t->townnametype = tnp.type;
 	}
 	t->townnameparts = townnameparts;
 
diff --git a/src/townname_type.h b/src/townname_type.h
--- a/src/townname_type.h
+++ b/src/townname_type.h
@@ -15,11 +15,14 @@
 
 #include "newgrf_townname.h"
 #include "town_type.h"
+#include "string_type.h"
 #include <set>
 #include <string>
 
 typedef std::set<std::string> TownNames;
 
+static constexpr uint BUILTIN_TOWNNAME_GENERATOR_COUNT = SPECSTR_TOWNNAME_LAST - SPECSTR_TOWNNAME_START + 1; ///< Number of built-in town name generators.
+
 /**
  * Struct holding parameters used to generate town name.
  * Speeds things up a bit because these values are computed only once per name generation.
@@ -34,10 +37,9 @@ struct TownNameParams {
 	 */
 	TownNameParams(byte town_name)
 	{
-		extern int _nb_orig_names;
-		bool grf = town_name >= _nb_orig_names;
-		this->grfid = grf ? GetGRFTownNameId(town_name - _nb_orig_names) : 0;
-		this->type = grf ? GetGRFTownNameType(town_name - _nb_orig_names) : SPECSTR_TOWNNAME_START + town_name;
+		bool grf = town_name >= BUILTIN_TOWNNAME_GENERATOR_COUNT;
+		this->grfid = grf ? GetGRFTownNameId(town_name - BUILTIN_TOWNNAME_GENERATOR_COUNT) : 0;
+		this->type = grf ? GetGRFTownNameType(town_name - BUILTIN_TOWNNAME_GENERATOR_COUNT) : SPECSTR_TOWNNAME_START + town_name;
 	}
 
 	TownNameParams(const Town *t);