diff --git a/sources/src/main/java/io/akarin/api/IMixinChunk.java b/sources/src/main/java/io/akarin/api/IMixinChunk.java
new file mode 100644
index 000000000..c33b1579c
--- /dev/null
+++ b/sources/src/main/java/io/akarin/api/IMixinChunk.java
@@ -0,0 +1,9 @@
+package io.akarin.api;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+public interface IMixinChunk {
+    AtomicInteger getPendingLightUpdates();
+    
+    long getLightUpdateTime();
+}
\ No newline at end of file
diff --git a/sources/src/main/java/io/akarin/server/mixin/lighting/MixinChunkProviderServer.java b/sources/src/main/java/io/akarin/server/mixin/lighting/MixinChunkProviderServer.java
new file mode 100644
index 000000000..31a6ffa2d
--- /dev/null
+++ b/sources/src/main/java/io/akarin/server/mixin/lighting/MixinChunkProviderServer.java
@@ -0,0 +1,27 @@
+package io.akarin.server.mixin.lighting;
+
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.Redirect;
+
+import io.akarin.api.IMixinChunk;
+import net.minecraft.server.ChunkProviderServer;
+import net.minecraft.server.WorldServer;
+
+@Mixin(value = ChunkProviderServer.class, remap = false, priority = 1001)
+public class MixinChunkProviderServer {
+    @Shadow @Final public WorldServer world;
+
+    @Redirect(method = "unloadChunks", at = @At(
+            value = "INVOKE",
+            target = "Lnet/minecraft/server/Chunk;isUnloading()Z"
+    ))
+    public boolean shouldUnload(IMixinChunk chunk) {
+        if (chunk.getPendingLightUpdates().get() > 0 || this.world.getTime() - chunk.getLightUpdateTime() < 20) {
+            return false;
+        }
+        return true;
+    }
+}
diff --git a/sources/src/main/java/net/minecraft/server/EntityTracker.java b/sources/src/main/java/net/minecraft/server/EntityTracker.java
index 168bb75f7..ad48af80b 100644
--- a/sources/src/main/java/net/minecraft/server/EntityTracker.java
+++ b/sources/src/main/java/net/minecraft/server/EntityTracker.java
@@ -11,6 +11,13 @@ import java.util.concurrent.locks.ReentrantReadWriteLock;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
+/**
+ * <b>Akarin Changes Note</b><br>
+ * <br>
+ * 1) Make entries-set concurrent<br>
+ * 2) Add lock for entries-set operations<br>
+ * @author cakoyo
+ */
 public class EntityTracker {
 
     private static final Logger a = LogManager.getLogger();