diff --git a/src/main/java/net/minecraftforge/installer/actions/OfflineAction.java b/src/main/java/net/minecraftforge/installer/actions/OfflineAction.java
index 7cd7fee..0f45d9a 100644
--- a/src/main/java/net/minecraftforge/installer/actions/OfflineAction.java
+++ b/src/main/java/net/minecraftforge/installer/actions/OfflineAction.java
@@ -78,6 +78,9 @@ public boolean run(File target, File installer) throws ActionCanceledException {
 
         checkCancel();
         try (ZipOutputStream zout = new ZipOutputStream(new FileOutputStream(target))) {
+            // Explicitly set compression level because of potential differences based on environment.
+            // See https://github.com/MinecraftForge/JarSplitter/pull/2
+            zout.setLevel(6);
             Set<String> seen = new HashSet<>();
 
             // Copy our input installer jar