diff --git a/cache/src/main/kotlin/org/openrs2/cache/DiskStore.kt b/cache/src/main/kotlin/org/openrs2/cache/DiskStore.kt
index 3c43f709..e34028a4 100644
--- a/cache/src/main/kotlin/org/openrs2/cache/DiskStore.kt
+++ b/cache/src/main/kotlin/org/openrs2/cache/DiskStore.kt
@@ -30,10 +30,13 @@ public class DiskStore private constructor(
     private val data: BufferedFileChannel,
     private val musicData: BufferedFileChannel?,
     private val indexes: Array<BufferedFileChannel?>,
-    private val alloc: ByteBufAllocator
+    private val alloc: ByteBufAllocator,
+    legacyData: Boolean
 ) : Store {
     private data class IndexEntry(val size: Int, val block: Int)
 
+    private val archiveOffset = if (legacyData) 1 else 0
+
     init {
         require(indexes.size == Store.MAX_ARCHIVE + 1)
     }
@@ -194,7 +197,7 @@ public class DiskStore private constructor(
                     }
                     val actualNum = tempBuf.readUnsignedShort()
                     val nextBlock = tempBuf.readUnsignedMedium()
-                    val actualArchive = tempBuf.readUnsignedByte().toInt()
+                    val actualArchive = (tempBuf.readUnsignedByte().toInt() - archiveOffset) and 0xFF
 
                     // verify header
                     when {
@@ -317,7 +320,7 @@ public class DiskStore private constructor(
                 }
                 val actualNum = tempBuf.readUnsignedShort()
                 nextBlock = tempBuf.readUnsignedMedium()
-                val actualArchive = tempBuf.readUnsignedByte().toInt()
+                val actualArchive = (tempBuf.readUnsignedByte().toInt() - archiveOffset) and 0xFF
 
                 if (actualGroup != group || actualNum != num || actualArchive != archive) {
                     block = 0
@@ -371,7 +374,7 @@ public class DiskStore private constructor(
                             }
                             val actualNum = tempBuf.readUnsignedShort()
                             nextNextBlock = tempBuf.readUnsignedMedium()
-                            val actualArchive = tempBuf.readUnsignedByte().toInt()
+                            val actualArchive = (tempBuf.readUnsignedByte().toInt() - archiveOffset) and 0xFF
 
                             if (actualGroup != group || actualNum != nextNum || actualArchive != archive) {
                                 nextBlock = 0
@@ -403,7 +406,7 @@ public class DiskStore private constructor(
                 }
                 tempBuf.writeShort(num)
                 tempBuf.writeMedium(nextBlock)
-                tempBuf.writeByte(archive)
+                tempBuf.writeByte(archive + archiveOffset)
 
                 data.write(blockPos, tempBuf, headerSize)
 
@@ -501,10 +504,13 @@ public class DiskStore private constructor(
             val js5DataPath = dataPath(root)
             val legacyDataPath = legacyDataPath(root)
 
-            val dataPath = if (Files.exists(js5DataPath)) {
-                js5DataPath
-            } else {
+            // We check for js5DataPath first as it takes precedence.
+            val legacyDataFile = !Files.exists(js5DataPath)
+
+            val dataPath = if (legacyDataFile) {
                 legacyDataPath
+            } else {
+                js5DataPath
             }
             val data = BufferedFileChannel(
                 FileChannel.open(dataPath, READ, WRITE),
@@ -539,17 +545,17 @@ public class DiskStore private constructor(
                 }
             }
 
-            return DiskStore(root, data, musicData, archives, alloc)
+            return DiskStore(root, data, musicData, archives, alloc, legacyDataFile)
         }
 
         public fun create(
             root: Path,
             alloc: ByteBufAllocator = ByteBufAllocator.DEFAULT,
-            legacyDataPath: Boolean = false
+            legacyDataFile: Boolean = false
         ): Store {
             Files.createDirectories(root)
 
-            val dataPath = if (legacyDataPath) {
+            val dataPath = if (legacyDataFile) {
                 legacyDataPath(root)
             } else {
                 dataPath(root)
@@ -563,7 +569,7 @@ public class DiskStore private constructor(
 
             val archives = Array<BufferedFileChannel?>(Store.MAX_ARCHIVE + 1) { null }
 
-            return DiskStore(root, data, null, archives, alloc)
+            return DiskStore(root, data, null, archives, alloc, legacyDataFile)
         }
     }
 }
diff --git a/cache/src/test/kotlin/org/openrs2/cache/DiskStoreTest.kt b/cache/src/test/kotlin/org/openrs2/cache/DiskStoreTest.kt
index 208d0dcc..d2bf6b9d 100644
--- a/cache/src/test/kotlin/org/openrs2/cache/DiskStoreTest.kt
+++ b/cache/src/test/kotlin/org/openrs2/cache/DiskStoreTest.kt
@@ -507,6 +507,12 @@ class DiskStoreTest {
             }
         }
 
+        readTest("corrupt-first-invalid-archive-legacy") { store ->
+            assertFailsWith<StoreCorruptException> {
+                store.read(0, 1).release()
+            }
+        }
+
         readTest("corrupt-first-invalid-block-number") { store ->
             assertFailsWith<StoreCorruptException> {
                 store.read(255, 1).release()
@@ -537,6 +543,12 @@ class DiskStoreTest {
             }
         }
 
+        readTest("corrupt-second-invalid-archive-legacy") { store ->
+            assertFailsWith<StoreCorruptException> {
+                store.read(0, 1).release()
+            }
+        }
+
         readTest("corrupt-second-invalid-block-number") { store ->
             assertFailsWith<StoreCorruptException> {
                 store.read(255, 1).release()
@@ -587,6 +599,15 @@ class DiskStoreTest {
             }
         }
 
+        overwriteTest(
+            "corrupt-first-invalid-archive-legacy",
+            "corrupt-first-invalid-archive-overwritten-legacy"
+        ) { store ->
+            copiedBuffer("Hello".repeat(300)).use { buf ->
+                store.write(0, 1, buf)
+            }
+        }
+
         overwriteTest("corrupt-first-invalid-block-number", "corrupt-first-invalid-block-number-overwritten") { store ->
             copiedBuffer("Hello".repeat(300)).use { buf ->
                 store.write(255, 1, buf)
@@ -617,6 +638,15 @@ class DiskStoreTest {
             }
         }
 
+        overwriteTest(
+            "corrupt-second-invalid-archive-legacy",
+            "corrupt-second-invalid-archive-overwritten-legacy"
+        ) { store ->
+            copiedBuffer("Hello".repeat(300)).use { buf ->
+                store.write(0, 1, buf)
+            }
+        }
+
         overwriteTest(
             "corrupt-second-invalid-block-number",
             "corrupt-second-invalid-block-number-overwritten"
@@ -665,6 +695,14 @@ class DiskStoreTest {
             }
         }
 
+        readTest("corrupt-first-invalid-archive-overwritten-legacy") { store ->
+            store.read(0, 1).use { actual ->
+                copiedBuffer("Hello".repeat(300)).use { expected ->
+                    assertEquals(expected, actual)
+                }
+            }
+        }
+
         readTest("corrupt-first-invalid-block-number-overwritten") { store ->
             store.read(255, 1).use { actual ->
                 copiedBuffer("Hello".repeat(300)).use { expected ->
@@ -705,6 +743,14 @@ class DiskStoreTest {
             }
         }
 
+        readTest("corrupt-second-invalid-archive-overwritten-legacy") { store ->
+            store.read(0, 1).use { actual ->
+                copiedBuffer("Hello".repeat(300)).use { expected ->
+                    assertEquals(expected, actual)
+                }
+            }
+        }
+
         readTest("corrupt-second-invalid-block-number-overwritten") { store ->
             store.read(255, 1).use { actual ->
                 copiedBuffer("Hello".repeat(300)).use { expected ->
@@ -762,9 +808,9 @@ class DiskStoreTest {
 
     @Test
     fun testCreateLegacyDataFile() {
-        writeTest("single-block-legacy", legacyDataPath = true) { store ->
+        writeTest("single-block-legacy", legacyDataFile = true) { store ->
             copiedBuffer("OpenRS2").use { buf ->
-                store.write(255, 1, buf)
+                store.write(0, 1, buf)
             }
         }
     }
@@ -773,7 +819,7 @@ class DiskStoreTest {
     fun testOpenLegacyDataFile() {
         readTest("single-block-legacy") { store ->
             copiedBuffer("OpenRS2").use { expected ->
-                store.read(255, 1).use { actual ->
+                store.read(0, 1).use { actual ->
                     assertEquals(expected, actual)
                 }
             }
@@ -786,10 +832,10 @@ class DiskStoreTest {
         }
     }
 
-    private fun writeTest(name: String, legacyDataPath: Boolean = false, f: (Store) -> Unit) {
+    private fun writeTest(name: String, legacyDataFile: Boolean = false, f: (Store) -> Unit) {
         Jimfs.newFileSystem(Configuration.forCurrentPlatform()).use { fs ->
             val actual = fs.rootDirectories.first().resolve("cache")
-            DiskStore.create(actual, legacyDataPath = legacyDataPath).use { store ->
+            DiskStore.create(actual, legacyDataFile = legacyDataFile).use { store ->
                 f(store)
             }
 
diff --git a/cache/src/test/resources/org/openrs2/cache/disk-store/corrupt-first-invalid-archive-legacy/main_file_cache.dat b/cache/src/test/resources/org/openrs2/cache/disk-store/corrupt-first-invalid-archive-legacy/main_file_cache.dat
new file mode 100644
index 00000000..7220e157
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diff --git a/cache/src/test/resources/org/openrs2/cache/disk-store/corrupt-first-invalid-archive-legacy/main_file_cache.idx0 b/cache/src/test/resources/org/openrs2/cache/disk-store/corrupt-first-invalid-archive-legacy/main_file_cache.idx0
new file mode 100644
index 00000000..fba8761c
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diff --git a/cache/src/test/resources/org/openrs2/cache/disk-store/corrupt-first-invalid-archive-overwritten-legacy/main_file_cache.dat b/cache/src/test/resources/org/openrs2/cache/disk-store/corrupt-first-invalid-archive-overwritten-legacy/main_file_cache.dat
new file mode 100644
index 00000000..653f74e4
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diff --git a/cache/src/test/resources/org/openrs2/cache/disk-store/corrupt-first-invalid-archive-overwritten-legacy/main_file_cache.idx0 b/cache/src/test/resources/org/openrs2/cache/disk-store/corrupt-first-invalid-archive-overwritten-legacy/main_file_cache.idx0
new file mode 100644
index 00000000..f7c437d5
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diff --git a/cache/src/test/resources/org/openrs2/cache/disk-store/corrupt-second-invalid-archive-legacy/main_file_cache.dat b/cache/src/test/resources/org/openrs2/cache/disk-store/corrupt-second-invalid-archive-legacy/main_file_cache.dat
new file mode 100644
index 00000000..9745254c
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diff --git a/cache/src/test/resources/org/openrs2/cache/disk-store/corrupt-second-invalid-archive-legacy/main_file_cache.idx0 b/cache/src/test/resources/org/openrs2/cache/disk-store/corrupt-second-invalid-archive-legacy/main_file_cache.idx0
new file mode 100644
index 00000000..fba8761c
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diff --git a/cache/src/test/resources/org/openrs2/cache/disk-store/corrupt-second-invalid-archive-overwritten-legacy/main_file_cache.dat b/cache/src/test/resources/org/openrs2/cache/disk-store/corrupt-second-invalid-archive-overwritten-legacy/main_file_cache.dat
new file mode 100644
index 00000000..93ca1146
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diff --git a/cache/src/test/resources/org/openrs2/cache/disk-store/corrupt-second-invalid-archive-overwritten-legacy/main_file_cache.idx0 b/cache/src/test/resources/org/openrs2/cache/disk-store/corrupt-second-invalid-archive-overwritten-legacy/main_file_cache.idx0
new file mode 100644
index 00000000..6c97b5aa
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diff --git a/cache/src/test/resources/org/openrs2/cache/disk-store/single-block-legacy/main_file_cache.dat b/cache/src/test/resources/org/openrs2/cache/disk-store/single-block-legacy/main_file_cache.dat
index 98a426d1..c7bc0906 100644
Binary files a/cache/src/test/resources/org/openrs2/cache/disk-store/single-block-legacy/main_file_cache.dat and b/cache/src/test/resources/org/openrs2/cache/disk-store/single-block-legacy/main_file_cache.dat differ
diff --git a/cache/src/test/resources/org/openrs2/cache/disk-store/single-block-legacy/main_file_cache.idx255 b/cache/src/test/resources/org/openrs2/cache/disk-store/single-block-legacy/main_file_cache.idx0
similarity index 100%
rename from cache/src/test/resources/org/openrs2/cache/disk-store/single-block-legacy/main_file_cache.idx255
rename to cache/src/test/resources/org/openrs2/cache/disk-store/single-block-legacy/main_file_cache.idx0