diff --git a/game-server/src/main/kotlin/work/fking/pangya/game/packet/handler/ClubSetUpgradePacketHandler.kt b/game-server/src/main/kotlin/work/fking/pangya/game/packet/handler/ClubSetUpgradePacketHandler.kt
index a15f54a..7e8a9e3 100644
--- a/game-server/src/main/kotlin/work/fking/pangya/game/packet/handler/ClubSetUpgradePacketHandler.kt
+++ b/game-server/src/main/kotlin/work/fking/pangya/game/packet/handler/ClubSetUpgradePacketHandler.kt
@@ -3,7 +3,6 @@ package work.fking.pangya.game.packet.handler
 import io.netty.buffer.ByteBuf
 import work.fking.pangya.game.GameServer
 import work.fking.pangya.game.net.ClientPacketHandler
-import work.fking.pangya.game.packet.outbound.ClubSetReplies
 import work.fking.pangya.game.player.Player
 import work.fking.pangya.game.player.statById
 import work.fking.pangya.game.task.ChangeClubSetStatTask
diff --git a/game-server/src/main/kotlin/work/fking/pangya/game/packet/outbound/ClubSetReplies.kt b/game-server/src/main/kotlin/work/fking/pangya/game/packet/outbound/ClubSetReplies.kt
deleted file mode 100644
index c4844c7..0000000
--- a/game-server/src/main/kotlin/work/fking/pangya/game/packet/outbound/ClubSetReplies.kt
+++ /dev/null
@@ -1,17 +0,0 @@
-package work.fking.pangya.game.packet.outbound
-
-import work.fking.pangya.networking.protocol.OutboundPacket
-
-object ClubSetReplies {
-
-    fun upgradeAck(type: Int, stat: Int, itemUid: Int, cost: Long): OutboundPacket {
-        return OutboundPacket { buffer ->
-            buffer.writeShortLE(0xa5)
-            buffer.writeByte(type)
-            buffer.writeByte(1) // 0 doesn't upgrade a clubset but 1 does?
-            buffer.writeByte(stat)
-            buffer.writeIntLE(itemUid)
-            buffer.writeLongLE(cost) // TODO: how to calculate the upgrade cost?
-        }
-    }
-}
\ No newline at end of file
diff --git a/game-server/src/main/kotlin/work/fking/pangya/game/packet/outbound/ClubSetUpgradeReplies.kt b/game-server/src/main/kotlin/work/fking/pangya/game/packet/outbound/ClubSetUpgradeReplies.kt
new file mode 100644
index 0000000..6e81f8e
--- /dev/null
+++ b/game-server/src/main/kotlin/work/fking/pangya/game/packet/outbound/ClubSetUpgradeReplies.kt
@@ -0,0 +1,26 @@
+package work.fking.pangya.game.packet.outbound
+
+import work.fking.pangya.networking.protocol.OutboundPacket
+
+object ClubSetUpgradeReplies {
+
+    fun upgradeAck(result: UpgradeResult, stat: Int, itemUid: Int, cost: Long = 0): OutboundPacket {
+        return OutboundPacket { buffer ->
+            buffer.writeShortLE(0xa5)
+            buffer.writeByte(result.code)
+            buffer.writeByte(1) // 0 doesn't upgrade a clubset but 1 does?
+            buffer.writeByte(stat)
+            buffer.writeIntLE(itemUid)
+            buffer.writeLongLE(cost)
+        }
+    }
+
+    enum class UpgradeResult(val code: Int) {
+        UPGRADE_SUCCESS(1),
+        DOWNGRADE_SUCCESS(2),
+        INSUFFICIENT_PANG(3),
+        INSUFFICIENT_SLOTS(4),
+        CANNOT_DOWNGRADE_ANYMORE(5),
+        FAILED_TO_UPGRADE(6)
+    }
+}
\ No newline at end of file
diff --git a/game-server/src/main/kotlin/work/fking/pangya/game/task/ChangeClubSetStatTask.kt b/game-server/src/main/kotlin/work/fking/pangya/game/task/ChangeClubSetStatTask.kt
index 8168e23..86ce683 100644
--- a/game-server/src/main/kotlin/work/fking/pangya/game/task/ChangeClubSetStatTask.kt
+++ b/game-server/src/main/kotlin/work/fking/pangya/game/task/ChangeClubSetStatTask.kt
@@ -2,7 +2,12 @@ package work.fking.pangya.game.task
 
 import work.fking.pangya.game.model.IFF_TYPE_CLUBSET
 import work.fking.pangya.game.model.iffTypeFromId
-import work.fking.pangya.game.packet.outbound.ClubSetReplies
+import work.fking.pangya.game.packet.outbound.ClubSetUpgradeReplies
+import work.fking.pangya.game.packet.outbound.ClubSetUpgradeReplies.UpgradeResult.CANNOT_DOWNGRADE_ANYMORE
+import work.fking.pangya.game.packet.outbound.ClubSetUpgradeReplies.UpgradeResult.DOWNGRADE_SUCCESS
+import work.fking.pangya.game.packet.outbound.ClubSetUpgradeReplies.UpgradeResult.INSUFFICIENT_PANG
+import work.fking.pangya.game.packet.outbound.ClubSetUpgradeReplies.UpgradeResult.INSUFFICIENT_SLOTS
+import work.fking.pangya.game.packet.outbound.ClubSetUpgradeReplies.UpgradeResult.UPGRADE_SUCCESS
 import work.fking.pangya.game.persistence.PersistenceContext
 import work.fking.pangya.game.player.Item
 import work.fking.pangya.game.player.Player
@@ -45,7 +50,10 @@ class ChangeClubSetStatTask(
             SPIN, CURVE -> 1900
         }
         val wallet = player.wallet
-        require(wallet.pangBalance >= cost) { "Player ${player.nickname} tried to upgrade an item but doesn't have enough pang" }
+
+        if (wallet.pangBalance < cost) {
+            player.writeAndFlush(ClubSetUpgradeReplies.upgradeAck(result = INSUFFICIENT_PANG, stat = stat.ordinal, itemUid = itemUid))
+        }
         // TODO: verify clubset upgrade limits
 
         persistenceCtx.transactional { tx ->
@@ -54,15 +62,18 @@ class ChangeClubSetStatTask(
             persistenceCtx.playerRepository.saveWallet(tx, player.uid, wallet)
             persistenceCtx.inventoryRepository.saveItem(tx, player.uid, clubSet)
         }
-        player.writeAndFlush(ClubSetReplies.upgradeAck(type, stat.ordinal, itemUid, cost))
+        player.writeAndFlush(ClubSetUpgradeReplies.upgradeAck(result = UPGRADE_SUCCESS, stat = stat.ordinal, itemUid = itemUid, cost = cost))
     }
 
     private fun downgrade(clubSet: Item) {
-        require(clubSet.stats[stat.ordinal] > 0) { "Player ${player.nickname} tried to downgrade an item but the stat is already at 0" }
+        if (clubSet.stats[stat.ordinal] <= 0) {
+            player.writeAndFlush(ClubSetUpgradeReplies.upgradeAck(result = CANNOT_DOWNGRADE_ANYMORE, stat = stat.ordinal, itemUid = itemUid))
+            return
+        }
 
         clubSet.stats[stat.ordinal]--
         persistenceCtx.inventoryRepository.saveItem(persistenceCtx.noTxContext(), player.uid, clubSet)
-        player.writeAndFlush(ClubSetReplies.upgradeAck(type, stat.ordinal, itemUid, 0))
+        player.writeAndFlush(ClubSetUpgradeReplies.upgradeAck(result = DOWNGRADE_SUCCESS, stat = stat.ordinal, itemUid = itemUid))
     }
 }