diff --git a/src/main/java/de/bixilon/minosoft/data/registries/biomes/Biome.kt b/src/main/java/de/bixilon/minosoft/data/registries/biomes/Biome.kt
index f34bb23bf..d815f76af 100644
--- a/src/main/java/de/bixilon/minosoft/data/registries/biomes/Biome.kt
+++ b/src/main/java/de/bixilon/minosoft/data/registries/biomes/Biome.kt
@@ -28,11 +28,11 @@ data class Biome(
     override val identifier: ResourceLocation,
     val temperature: Float,
     val downfall: Float,
-    val skyColor: RGBColor?,
+    val skyColor: RGBColor? = null,
     val fogColor: RGBColor? = null,
-    val waterColor: RGBColor?,
-    val waterFogColor: RGBColor?,
-    val precipitation: BiomePrecipitation?,
+    val waterColor: RGBColor? = null,
+    val waterFogColor: RGBColor? = null,
+    val precipitation: BiomePrecipitation? = null,
 ) : RegistryItem() {
     val grassColorModifier = GrassColorModifiers.BIOME_MAP[identifier]
     val temperatureColorMapCoordinate = getColorMapCoordinate(temperature)
diff --git a/src/test/java/de/bixilon/minosoft/data/registries/biomes/BiomeTest.kt b/src/test/java/de/bixilon/minosoft/data/registries/biomes/BiomeTest.kt
new file mode 100644
index 000000000..58560be4b
--- /dev/null
+++ b/src/test/java/de/bixilon/minosoft/data/registries/biomes/BiomeTest.kt
@@ -0,0 +1,27 @@
+/*
+ * Minosoft
+ * Copyright (C) 2020-2023 Moritz Zwerger
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with this program. If not, see <https://www.gnu.org/licenses/>.
+ *
+ * This software is not affiliated with Mojang AB, the original developer of Minecraft.
+ */
+
+package de.bixilon.minosoft.data.registries.biomes
+
+import de.bixilon.minosoft.data.registries.identified.Namespaces.minecraft
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+class BiomeTest {
+
+    @Test
+    fun `color map index`() {
+        val biome = Biome(minecraft("plains"), temperature = 0.8f, downfall = 0.4f)
+        assertEquals(biome.colorMapPixelIndex, 44338)
+    }
+}