diff --git a/src/main/java/net/p3pp3rf1y/sophisticatedstorage/upgrades/hopper/HopperUpgradeWrapper.java b/src/main/java/net/p3pp3rf1y/sophisticatedstorage/upgrades/hopper/HopperUpgradeWrapper.java
index 02902101..0a573232 100644
--- a/src/main/java/net/p3pp3rf1y/sophisticatedstorage/upgrades/hopper/HopperUpgradeWrapper.java
+++ b/src/main/java/net/p3pp3rf1y/sophisticatedstorage/upgrades/hopper/HopperUpgradeWrapper.java
@@ -226,12 +226,12 @@ public void setPushingTo(Direction direction, boolean isPushing) {
 	}
 
 	private void serializePullDirections() {
-		upgrade.set(ModDataComponents.PULL_DIRECTIONS, pullDirections);
+		upgrade.set(ModDataComponents.PULL_DIRECTIONS, Set.copyOf(pullDirections));
 		save();
 	}
 
 	private void serializePushDirections() {
-		upgrade.set(ModDataComponents.PUSH_DIRECTIONS, pushDirections);
+		upgrade.set(ModDataComponents.PUSH_DIRECTIONS, Set.copyOf(pushDirections));
 		save();
 	}