Index: ps/trunk/binaries/data/mods/public/gui/gamesettings/attributes/Biome.js
===================================================================
--- ps/trunk/binaries/data/mods/public/gui/gamesettings/attributes/Biome.js	(revision 25646)
+++ ps/trunk/binaries/data/mods/public/gui/gamesettings/attributes/Biome.js	(revision 25647)
@@ -1,85 +1,93 @@
 GameSettings.prototype.Attributes.Biome = class Biome extends GameSetting
 {
 	init()
 	{
 		this.biomes = loadBiomes();
 		this.biomeData = {};
 		for (const biome of this.biomes)
 			this.biomeData[biome.Id] = biome;
 		this.cachedMapData = undefined;
 
 		this.biome = undefined;
 		// NB: random is always available.
 		this.available = new Set();
 
 		this.settings.map.watch(() => this.onMapChange(), ["map"]);
 	}
 
 	toInitAttributes(attribs)
 	{
 		if (!this.biome)
 			return;
 		attribs.settings.Biome = this.biome;
 	}
 
 	fromInitAttributes(attribs)
 	{
 		if (!this.getLegacySetting(attribs, "Biome"))
 			this.setBiome(undefined);
 		else
 			this.setBiome(this.getLegacySetting(attribs, "Biome"));
 	}
 
+	filterBiome(available)
+	{
+		if (typeof available === "string")
+			return biome => biome.Id.startsWith(available);
+
+		return biome => available.indexOf(biome.Id) !== -1;
+	}
+
 	onMapChange()
 	{
 		const mapData = this.settings.map.data;
 		if (mapData && mapData.settings && mapData.settings.SupportedBiomes !== undefined)
 		{
 			if (mapData.settings.SupportedBiomes === this.cachedMapData)
 				return;
 			this.cachedMapData = mapData.settings.SupportedBiomes;
-			this.available = new Set(this.biomes.filter(biome => biome.Id.indexOf(mapData.settings.SupportedBiomes) !== -1)
+			this.available = new Set(this.biomes.filter(this.filterBiome(mapData.settings.SupportedBiomes))
 				.map(biome => biome.Id));
 			this.biome = "random";
 		}
 		else if (this.cachedMapData !== undefined)
 		{
 			this.cachedMapData = undefined;
 			this.available = new Set();
 			this.biome = undefined;
 		}
 	}
 
 	setBiome(biome)
 	{
 		// TODO: more validation.
 		if (this.available.size)
 			this.biome = biome || "random";
 		else
 			this.biome = undefined;
 	}
 
 	getAvailableBiomeData()
 	{
 		return Array.from(this.available).map(biome => this.biomeData[biome]);
 	}
 
 	getData()
 	{
 		if (!this.biome)
 			return undefined;
 		return this.biomeData[this.biome];
 	}
 
 	pickRandomItems()
 	{
 		// If the map is random, we need to wait until it selects to know if we need to pick a biome.
 		if (this.settings.map.map === "random")
 			return true;
 
 		if (this.biome !== "random")
 			return false;
 		this.biome = pickRandom(Array.from(this.available));
 		return true;
 	}
 };