diff --git a/build.gradle.kts b/build.gradle.kts
index bec4d26..3affa9e 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -8,7 +8,7 @@ plugins {
     kotlin("jvm") version "2.1.0"
     java
     id("org.jetbrains.dokka").version("1.9.20")
-    id("com.gradleup.shadow").version("9.0.0-beta16")
+    id("com.gradleup.shadow").version("9.3.0")
     // Maven publish
     `maven-publish`
     signing
@@ -18,7 +18,7 @@ plugins {
 }
 
 group = "xyz.alexcrea"
-version = "1.15.7"
+version = "1.15.8"
 
 val effectiveVersion = "$version" +
         (if (System.getenv("SMALL_COMMIT_HASH") != null) "-dev-${System.getenv("SMALL_COMMIT_HASH")!!}" else "")
diff --git a/nms/nms-common/src/main/kotlin/xyz/alexcrea/cuanvil/dependency/gui/ExternGuiTester.kt b/nms/nms-common/src/main/kotlin/xyz/alexcrea/cuanvil/dependency/gui/ExternGuiTester.kt
index 029e4a7..8b06b10 100644
--- a/nms/nms-common/src/main/kotlin/xyz/alexcrea/cuanvil/dependency/gui/ExternGuiTester.kt
+++ b/nms/nms-common/src/main/kotlin/xyz/alexcrea/cuanvil/dependency/gui/ExternGuiTester.kt
@@ -1,17 +1,16 @@
 package xyz.alexcrea.cuanvil.dependency.gui
 
 import org.bukkit.inventory.InventoryView
-import xyz.alexcrea.cuanvil.dependency.util.PlatformUtil
 
 interface ExternGuiTester {
 
     fun getContainerClass(view: InventoryView): Class<Any>?
 
     fun testIfGui(inventory: InventoryView): Boolean {
-        // container class only allow default bukkit craft view class
+        // container class only allow default bukkit craft view or test class
 
         val clazz = getContainerClass(inventory)
-        return clazz != null
+        return clazz == null
     }
 
 }
\ No newline at end of file
diff --git a/src/main/kotlin/xyz/alexcrea/cuanvil/dependency/gui/GenericExternGuiTester.kt b/src/main/kotlin/xyz/alexcrea/cuanvil/dependency/gui/GenericExternGuiTester.kt
index 85e32d5..4ff3354 100644
--- a/src/main/kotlin/xyz/alexcrea/cuanvil/dependency/gui/GenericExternGuiTester.kt
+++ b/src/main/kotlin/xyz/alexcrea/cuanvil/dependency/gui/GenericExternGuiTester.kt
@@ -1,7 +1,6 @@
 package xyz.alexcrea.cuanvil.dependency.gui
 
 import org.bukkit.inventory.InventoryView
-import xyz.alexcrea.cuanvil.dependency.MinecraftVersionUtil
 import java.lang.reflect.Method
 
 class GenericExternGuiTester: ExternGuiTester {
@@ -12,14 +11,16 @@ class GenericExternGuiTester: ExternGuiTester {
         private const val HANDLE_METHOD_NAME = "getHandle"
     }
 
-    var tested = false
+    var testExist = false
+    var inTesting = false
 
     var testedClass: String? = null
     lateinit var getHandleMethod: Method
 
     override fun getContainerClass(view: InventoryView): Class<Any>? {
         // In case we are in a test environment
-        if(!tested) testClassExist()
+        if(!testExist) testClassExist()
+        if(inTesting) return view.javaClass //TEMPORARY
 
         if(!testedClass.contentEquals(view.javaClass.name))
             return null
@@ -36,7 +37,7 @@ class GenericExternGuiTester: ExternGuiTester {
     }
 
     fun testClassExist() {
-        tested = true
+        testExist = true
 
         // We first try to get craft anvil interface,
         // but is absent on old version so we try craft inventory view before
@@ -53,6 +54,8 @@ class GenericExternGuiTester: ExternGuiTester {
         }
         catch (_: ClassNotFoundException) {}
         catch (_: NoSuchMethodException) {}
+
+        inTesting = true
     }
 
 }
\ No newline at end of file