Paper/nms-patches/BiomeStorage.patch

--- a/net/minecraft/server/BiomeStorage.java
+++ b/net/minecraft/server/BiomeStorage.java
@@ -87,4 +87,14 @@
 
         return this.h[i1 << BiomeStorage.e + BiomeStorage.e | j1 << BiomeStorage.e | l];
     }
+
+    // CraftBukkit start
+    public void setBiome(int i, int j, int k, BiomeBase biome) {
+        int l = i & BiomeStorage.b;
+        int i1 = MathHelper.clamp(j, 0, BiomeStorage.c);
+        int j1 = k & BiomeStorage.b;
+
+        this.h[i1 << BiomeStorage.e + BiomeStorage.e | j1 << BiomeStorage.e | l] = biome;
+    }
+    // CraftBukkit end
 }