diff --git a/src/main/java/com/falsepattern/endlessids/mixin/mixins/common/vanilla/worldgen/GenLayerRiverMixMixin.java b/src/main/java/com/falsepattern/endlessids/mixin/mixins/common/vanilla/worldgen/GenLayerRiverMixMixin.java
new file mode 100644
index 0000000..d117c46
--- /dev/null
+++ b/src/main/java/com/falsepattern/endlessids/mixin/mixins/common/vanilla/worldgen/GenLayerRiverMixMixin.java
@@ -0,0 +1,18 @@
+package com.falsepattern.endlessids.mixin.mixins.common.vanilla.worldgen;
+
+import com.falsepattern.endlessids.constants.ExtendedConstants;
+import com.falsepattern.endlessids.constants.VanillaConstants;
+import net.minecraft.world.gen.layer.GenLayerRiverMix;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.Constant;
+import org.spongepowered.asm.mixin.injection.ModifyConstant;
+
+@Mixin(GenLayerRiverMix.class)
+public abstract class GenLayerRiverMixMixin {
+    @ModifyConstant(method = "getInts",
+                    constant = @Constant(intValue = VanillaConstants.biomeIDMask),
+                    require = 1)
+    private int extendTheID(int constant) {
+        return ExtendedConstants.biomeIDMask;
+    }
+}
diff --git a/src/main/java/com/falsepattern/endlessids/mixin/mixins/common/vanilla/worldgen/GenLayerVoronoiZoomMixin.java b/src/main/java/com/falsepattern/endlessids/mixin/mixins/common/vanilla/worldgen/GenLayerVoronoiZoomMixin.java
new file mode 100644
index 0000000..33ac575
--- /dev/null
+++ b/src/main/java/com/falsepattern/endlessids/mixin/mixins/common/vanilla/worldgen/GenLayerVoronoiZoomMixin.java
@@ -0,0 +1,19 @@
+package com.falsepattern.endlessids.mixin.mixins.common.vanilla.worldgen;
+
+import com.falsepattern.endlessids.constants.ExtendedConstants;
+import com.falsepattern.endlessids.constants.VanillaConstants;
+import net.minecraft.world.gen.layer.GenLayerRiverMix;
+import net.minecraft.world.gen.layer.GenLayerVoronoiZoom;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.Constant;
+import org.spongepowered.asm.mixin.injection.ModifyConstant;
+
+@Mixin(GenLayerVoronoiZoom.class)
+public abstract class GenLayerVoronoiZoomMixin {
+    @ModifyConstant(method = "getInts",
+                    constant = @Constant(intValue = VanillaConstants.biomeIDMask),
+                    require = 2)
+    private int extendTheID(int constant) {
+        return ExtendedConstants.biomeIDMask;
+    }
+}