diff --git a/src/main/java/net/runelite/cache/fs/DataFile.java b/src/main/java/net/runelite/cache/fs/DataFile.java
index 8ad21537c0..f006b1c2ce 100644
--- a/src/main/java/net/runelite/cache/fs/DataFile.java
+++ b/src/main/java/net/runelite/cache/fs/DataFile.java
@@ -139,7 +139,7 @@ public class DataFile implements Closeable
 		int sector;
 		int startSector;
 		
-		sector = (int) ((this.dat.length() + 519L) / 520L);
+		sector = (int) ((dat.length() + (long) (SECTOR_SIZE - 1)) / (long) SECTOR_SIZE);
 		if (sector == 0)
 		{
 			sector = 1;
@@ -153,7 +153,7 @@ public class DataFile implements Closeable
 
 			if (nextSector == 0)
 			{
-				nextSector = (int) ((dat.length() + 519L) / 520L);
+				nextSector = (int) ((dat.length() + (long) (SECTOR_SIZE - 1)) / (long) SECTOR_SIZE);
 				if (nextSector == 0)
 				{
 					++nextSector;
@@ -165,13 +165,14 @@ public class DataFile implements Closeable
 				}
 			}
 
-			if (data.remaining() <= 512)
-			{
-				nextSector = 0;
-			}
 
 			if (0xFFFF < archiveId)
 			{
+				if (data.remaining() <= 510)
+				{
+					nextSector = 0;
+				}
+			
 				this.readCachedBuffer[0] = (byte) (archiveId >> 24);
 				this.readCachedBuffer[1] = (byte) (archiveId >> 16);
 				this.readCachedBuffer[2] = (byte) (archiveId >> 8);
@@ -193,6 +194,11 @@ public class DataFile implements Closeable
 			}
 			else
 			{
+				if (data.remaining() <= 512)
+				{
+					nextSector = 0;
+				}
+			
 				this.readCachedBuffer[0] = (byte) (archiveId >> 8);
 				this.readCachedBuffer[1] = (byte) archiveId;
 				this.readCachedBuffer[2] = (byte) (part >> 8);
diff --git a/src/main/java/net/runelite/cache/fs/IndexEntry.java b/src/main/java/net/runelite/cache/fs/IndexEntry.java
index 56215c7919..19f3845dae 100644
--- a/src/main/java/net/runelite/cache/fs/IndexEntry.java
+++ b/src/main/java/net/runelite/cache/fs/IndexEntry.java
@@ -4,8 +4,8 @@ import java.util.Objects;
 
 public class IndexEntry
 {
-	private IndexFile indexFile;
-	private int id, sector, length;
+	private final IndexFile indexFile;
+	private final int id, sector, length;
 
 	public IndexEntry(IndexFile indexFile, int id, int sector, int length)
 	{