diff --git a/util/src/main/java/dev/openrs2/util/io/DeterministicJarOutputStream.kt b/util/src/main/java/dev/openrs2/util/io/DeterministicJarOutputStream.kt
index ce2e0bc7..71d2a479 100644
--- a/util/src/main/java/dev/openrs2/util/io/DeterministicJarOutputStream.kt
+++ b/util/src/main/java/dev/openrs2/util/io/DeterministicJarOutputStream.kt
@@ -4,12 +4,17 @@ import java.io.OutputStream
 import java.nio.file.attribute.FileTime
 import java.util.jar.JarOutputStream
 import java.util.jar.Manifest
+import java.util.zip.Deflater
 import java.util.zip.ZipEntry
 
 class DeterministicJarOutputStream : JarOutputStream {
     constructor(out: OutputStream) : super(out)
     constructor(out: OutputStream, man: Manifest) : super(out, man)
 
+    init {
+        setLevel(Deflater.BEST_COMPRESSION)
+    }
+
     override fun putNextEntry(ze: ZipEntry) {
         ze.creationTime = UNIX_EPOCH
         ze.lastAccessTime = UNIX_EPOCH