diff --git a/src/town_cmd.cpp b/src/town_cmd.cpp
index 09ca7cee97..fd380a8271 100644
--- a/src/town_cmd.cpp
+++ b/src/town_cmd.cpp
@@ -1901,6 +1901,7 @@ bool GenerateTowns(TownLayout layout)
 	uint total = (difficulty == (uint)CUSTOM_TOWN_NUMBER_DIFFICULTY) ? _settings_game.game_creation.custom_town_number : ScaleByMapSize(_num_initial_towns[difficulty] + (Random() & 7));
 	total = min(TownPool::MAX_SIZE, total);
 	uint32 townnameparts;
+	TownNames town_names;
 
 	SetGeneratingWorldProgress(GWP_TOWN, total);
 
@@ -1919,11 +1920,13 @@ bool GenerateTowns(TownLayout layout)
 		bool city = (_settings_game.economy.larger_towns != 0 && Chance16(1, _settings_game.economy.larger_towns));
 		IncreaseGeneratingWorldProgress(GWP_TOWN);
 		/* Get a unique name for the town. */
-		if (!GenerateTownName(&townnameparts)) continue;
+		if (!GenerateTownName(&townnameparts, &town_names)) continue;
 		/* try 20 times to create a random-sized town for the first loop. */
 		if (CreateRandomTown(20, townnameparts, TSZ_RANDOM, city, layout) != NULL) current_number++; // If creation was successful, raise a flag.
 	} while (--total);
 
+	town_names.clear();
+
 	if (current_number != 0) return true;
 
 	/* If current_number is still zero at this point, it means that not a single town has been created.
diff --git a/src/townname.cpp b/src/townname.cpp
index 495fde4b45..136882103a 100644
--- a/src/townname.cpp
+++ b/src/townname.cpp
@@ -75,9 +75,10 @@ char *GetTownName(char *buff, const Town *t, const char *last)
  * Verifies the town name is valid and unique.
  * @param r random bits
  * @param par town name parameters
+ * @param town_names if a name is generated, check its uniqueness with the set
  * @return true iff name is valid and unique
  */
-bool VerifyTownName(uint32 r, const TownNameParams *par)
+bool VerifyTownName(uint32 r, const TownNameParams *par, TownNames *town_names)
 {
 	/* reserve space for extra unicode character and terminating '\0' */
 	char buf1[(MAX_LENGTH_TOWN_NAME_CHARS + 1) * MAX_CHAR_LENGTH];
@@ -88,16 +89,21 @@ bool VerifyTownName(uint32 r, const TownNameParams *par)
 	/* Check size and width */
 	if (Utf8StringLength(buf1) >= MAX_LENGTH_TOWN_NAME_CHARS) return false;
 
-	const Town *t;
-	FOR_ALL_TOWNS(t) {
-		/* We can't just compare the numbers since
-		 * several numbers may map to a single name. */
-		const char *buf = t->name;
-		if (buf == NULL) {
-			GetTownName(buf2, t, lastof(buf2));
-			buf = buf2;
+	if (town_names != NULL) {
+		if (town_names->find(buf1) != town_names->end()) return false;
+		town_names->insert(buf1);
+	} else {
+		const Town *t;
+		FOR_ALL_TOWNS(t) {
+			/* We can't just compare the numbers since
+			 * several numbers may map to a single name. */
+			const char *buf = t->name;
+			if (buf == NULL) {
+				GetTownName(buf2, t, lastof(buf2));
+				buf = buf2;
+			}
+			if (strcmp(buf1, buf) == 0) return false;
 		}
-		if (strcmp(buf1, buf) == 0) return false;
 	}
 
 	return true;
@@ -107,9 +113,10 @@ bool VerifyTownName(uint32 r, const TownNameParams *par)
 /**
  * Generates valid town name.
  * @param townnameparts if a name is generated, it's stored there
+ * @param town_names if a name is generated, check its uniqueness with the set
  * @return true iff a name was generated
  */
-bool GenerateTownName(uint32 *townnameparts)
+bool GenerateTownName(uint32 *townnameparts, TownNames *town_names)
 {
 	/* Do not set too low tries, since when we run out of names, we loop
 	 * for #tries only one time anyway - then we stop generating more
@@ -120,7 +127,7 @@ bool GenerateTownName(uint32 *townnameparts)
 
 	for (int i = 1000; i != 0; i--) {
 		uint32 r = _generating_world ? Random() : InteractiveRandom();
-		if (!VerifyTownName(r, &par)) continue;
+		if (!VerifyTownName(r, &par, town_names)) continue;
 
 		*townnameparts = r;
 		return true;
diff --git a/src/townname_func.h b/src/townname_func.h
index 0925569786..409993e42a 100644
--- a/src/townname_func.h
+++ b/src/townname_func.h
@@ -17,7 +17,7 @@
 char *GenerateTownNameString(char *buf, const char *last, size_t lang, uint32 seed);
 char *GetTownName(char *buff, const TownNameParams *par, uint32 townnameparts, const char *last);
 char *GetTownName(char *buff, const Town *t, const char *last);
-bool VerifyTownName(uint32 r, const TownNameParams *par);
-bool GenerateTownName(uint32 *townnameparts);
+bool VerifyTownName(uint32 r, const TownNameParams *par, TownNames *town_names = NULL);
+bool GenerateTownName(uint32 *townnameparts, TownNames *town_names = NULL);
 
 #endif /* TOWNNAME_FUNC_H */
diff --git a/src/townname_type.h b/src/townname_type.h
index 8a4b12b8bf..0177294d99 100644
--- a/src/townname_type.h
+++ b/src/townname_type.h
@@ -17,6 +17,10 @@
 
 #include "newgrf_townname.h"
 #include "town_type.h"
+#include <set>
+#include <string>
+
+typedef std::set<std::string> TownNames;
 
 /**
  * Struct holding a parameters used to generate town name.