diff --git a/cache/src/main/kotlin/org/openrs2/cache/Js5MasterIndex.kt b/cache/src/main/kotlin/org/openrs2/cache/Js5MasterIndex.kt
index 8107dc94..30a0b09b 100644
--- a/cache/src/main/kotlin/org/openrs2/cache/Js5MasterIndex.kt
+++ b/cache/src/main/kotlin/org/openrs2/cache/Js5MasterIndex.kt
@@ -31,8 +31,10 @@ public inline class Js5MasterIndex(public val entries: MutableList<Entry> = muta
 
                 val entry = store.read(Js5Archive.ARCHIVESET, archive).use { buf ->
                     val checksum = buf.crc32()
-                    val version = Js5Index.read(buf).version
-                    // TODO(gpe): should we throw an exception if there are trailing bytes here?
+                    val version = Js5Compression.uncompress(buf).use { uncompressed ->
+                        Js5Index.read(uncompressed).version
+                    }
+                    // TODO(gpe): should we throw an exception if there are trailing bytes here or in the block above?
                     Entry(version, checksum)
                 }
 
diff --git a/cache/src/test/kotlin/org/openrs2/cache/Js5MasterIndexTest.kt b/cache/src/test/kotlin/org/openrs2/cache/Js5MasterIndexTest.kt
index 443cbb43..39b99e43 100644
--- a/cache/src/test/kotlin/org/openrs2/cache/Js5MasterIndexTest.kt
+++ b/cache/src/test/kotlin/org/openrs2/cache/Js5MasterIndexTest.kt
@@ -27,13 +27,13 @@ object Js5MasterIndexTest {
         assertEquals(
             Js5MasterIndex(
                 mutableListOf(
-                    Js5MasterIndex.Entry(0, 379203374),
-                    Js5MasterIndex.Entry(0x12345678, -717247318),
+                    Js5MasterIndex.Entry(0, 609698396),
+                    Js5MasterIndex.Entry(0x12345678, 78747481),
                     Js5MasterIndex.Entry(0, 0),
-                    Js5MasterIndex.Entry(0x9ABCDEF0.toInt(), 895417101),
+                    Js5MasterIndex.Entry(0x9ABCDEF0.toInt(), -456081154),
                     Js5MasterIndex.Entry(0, 0),
                     Js5MasterIndex.Entry(0, 0),
-                    Js5MasterIndex.Entry(0xAA55AA55.toInt(), -627983571)
+                    Js5MasterIndex.Entry(0xAA55AA55.toInt(), 186613982)
                 )
             ), index
         )
diff --git a/cache/src/test/resources/org/openrs2/cache/master-index/255/0.dat b/cache/src/test/resources/org/openrs2/cache/master-index/255/0.dat
index a786e127..8b4eb145 100644
Binary files a/cache/src/test/resources/org/openrs2/cache/master-index/255/0.dat and b/cache/src/test/resources/org/openrs2/cache/master-index/255/0.dat differ
diff --git a/cache/src/test/resources/org/openrs2/cache/master-index/255/1.dat b/cache/src/test/resources/org/openrs2/cache/master-index/255/1.dat
index a8c24c5d..23d831e4 100644
Binary files a/cache/src/test/resources/org/openrs2/cache/master-index/255/1.dat and b/cache/src/test/resources/org/openrs2/cache/master-index/255/1.dat differ
diff --git a/cache/src/test/resources/org/openrs2/cache/master-index/255/3.dat b/cache/src/test/resources/org/openrs2/cache/master-index/255/3.dat
index 540f4779..b8ff04cc 100644
Binary files a/cache/src/test/resources/org/openrs2/cache/master-index/255/3.dat and b/cache/src/test/resources/org/openrs2/cache/master-index/255/3.dat differ
diff --git a/cache/src/test/resources/org/openrs2/cache/master-index/255/6.dat b/cache/src/test/resources/org/openrs2/cache/master-index/255/6.dat
index 35a00753..c44e92a3 100644
Binary files a/cache/src/test/resources/org/openrs2/cache/master-index/255/6.dat and b/cache/src/test/resources/org/openrs2/cache/master-index/255/6.dat differ