diff --git a/gradle.properties b/gradle.properties
index 2e862b0..9b20745 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -1,5 +1,5 @@
 org.gradle.caching=true
 org.gradle.parallel=true
 org.gradle.jvmargs='-Dfile.encoding=UTF-8'
-projectVersion=1.5.4
+projectVersion=1.5.3
 libsPackage=team.devblook.akropolis.libs
diff --git a/src/main/java/team/devblook/akropolis/inventory/AbstractInventory.java b/src/main/java/team/devblook/akropolis/inventory/AbstractInventory.java
index e02d22f..622bf40 100644
--- a/src/main/java/team/devblook/akropolis/inventory/AbstractInventory.java
+++ b/src/main/java/team/devblook/akropolis/inventory/AbstractInventory.java
@@ -100,7 +100,7 @@ public List<UUID> getOpenInventories() {
 
     @EventHandler
     public void onInventoryClose(InventoryCloseEvent event) {
-        if (event.getView().getTopInventory().getHolder() instanceof InventoryBuilder && refreshEnabled) {
+        if (InventoryManager.getTopInventory(event).getHolder() instanceof InventoryBuilder && refreshEnabled) {
             openInventories.remove(event.getPlayer().getUniqueId());
         }
     }
diff --git a/src/main/java/team/devblook/akropolis/inventory/InventoryListener.java b/src/main/java/team/devblook/akropolis/inventory/InventoryListener.java
index 1515cad..f85594f 100644
--- a/src/main/java/team/devblook/akropolis/inventory/InventoryListener.java
+++ b/src/main/java/team/devblook/akropolis/inventory/InventoryListener.java
@@ -30,7 +30,7 @@ public class InventoryListener implements Listener {
 
     @EventHandler
     public void onInventoryClick(InventoryClickEvent event) {
-        if (event.getView().getTopInventory().getHolder() instanceof InventoryBuilder) {
+        if (InventoryManager.getTopInventory(event).getHolder() instanceof InventoryBuilder) {
             event.setCancelled(true);
 
             if (event.getWhoClicked() instanceof Player player) {
@@ -40,7 +40,7 @@ public void onInventoryClick(InventoryClickEvent event) {
                 if (itemStack == null || itemStack.getType() == Material.AIR)
                     return;
 
-                InventoryBuilder customHolder = (InventoryBuilder) event.getView().getTopInventory().getHolder();
+                InventoryBuilder customHolder = (InventoryBuilder) InventoryManager.getTopInventory(event).getHolder();
                 InventoryItem item = customHolder.getIcon(event.getRawSlot());
 
                 if (item == null)
diff --git a/src/main/java/team/devblook/akropolis/inventory/InventoryManager.java b/src/main/java/team/devblook/akropolis/inventory/InventoryManager.java
index 6f4f172..10d7d26 100644
--- a/src/main/java/team/devblook/akropolis/inventory/InventoryManager.java
+++ b/src/main/java/team/devblook/akropolis/inventory/InventoryManager.java
@@ -22,10 +22,14 @@
 import org.bukkit.Bukkit;
 import org.bukkit.configuration.file.YamlConfiguration;
 import org.bukkit.entity.Player;
+import org.bukkit.event.inventory.InventoryEvent;
+import org.bukkit.inventory.Inventory;
 import team.devblook.akropolis.AkropolisPlugin;
 import team.devblook.akropolis.inventory.inventories.CustomGUI;
 
 import java.io.*;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.UUID;
@@ -114,6 +118,17 @@ private void loadCustomMenus() {
         }
     }
 
+    public static Inventory getTopInventory(InventoryEvent event) {
+        try {
+            Object view = event.getView();
+            Method getTopInventory = view.getClass().getMethod("getTopInventory");
+            getTopInventory.setAccessible(true);
+            return (Inventory) getTopInventory.invoke(view);
+        } catch (NoSuchMethodException | InvocationTargetException | IllegalAccessException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
     public Map<String, AbstractInventory> getInventories() {
         return inventories;
     }
diff --git a/src/main/java/team/devblook/akropolis/util/ItemStackBuilder.java b/src/main/java/team/devblook/akropolis/util/ItemStackBuilder.java
index b556ac5..0b5d39f 100644
--- a/src/main/java/team/devblook/akropolis/util/ItemStackBuilder.java
+++ b/src/main/java/team/devblook/akropolis/util/ItemStackBuilder.java
@@ -48,7 +48,12 @@ public class ItemStackBuilder {
         // Fix: unknown "ARROW_INFINITE" field on versions 1.20.6 or newer.
         try {
             // 1.20.6 -> 206
-            final int version = Integer.parseInt(Bukkit.getMinecraftVersion().substring(2).replace(".", ""));
+            String strippedVersion = Bukkit.getMinecraftVersion()
+                    .substring(2)
+                    .replace(".", "");
+            // 1.21 -> 21 -> 210
+            int version = Integer.parseInt(strippedVersion.length() == 2 ? strippedVersion + "0" : strippedVersion);
+
             Field field = null;
             // This would correspond to check if the version is higher or equals to
             // 1.20.6.