diff --git a/src/Module/Exception/ModuleActivationException.php b/src/Module/Exception/ModuleActivationException.php
index 5178b8a..ccc51f9 100644
--- a/src/Module/Exception/ModuleActivationException.php
+++ b/src/Module/Exception/ModuleActivationException.php
@@ -13,7 +13,7 @@
 
 final class ModuleActivationException extends NotFound
 {
-    public const EXCEPTION_MESSAGE = "An error occurred while activating the module.";
+    private const EXCEPTION_MESSAGE = "An error occurred while activating the module.";
 
     public function __construct()
     {
diff --git a/src/Module/Exception/ModuleDeactivationException.php b/src/Module/Exception/ModuleDeactivationException.php
index 68fc0b8..553084c 100644
--- a/src/Module/Exception/ModuleDeactivationException.php
+++ b/src/Module/Exception/ModuleDeactivationException.php
@@ -13,7 +13,7 @@
 
 final class ModuleDeactivationException extends NotFound
 {
-    public const EXCEPTION_MESSAGE = "An error occurred while deactivating the module.";
+    private const EXCEPTION_MESSAGE = "An error occurred while deactivating the module.";
 
     public function __construct()
     {
diff --git a/tests/Unit/Module/Exception/ModuleActivationExceptionTest.php b/tests/Unit/Module/Exception/ModuleActivationExceptionTest.php
index 554366e..5598cc3 100644
--- a/tests/Unit/Module/Exception/ModuleActivationExceptionTest.php
+++ b/tests/Unit/Module/Exception/ModuleActivationExceptionTest.php
@@ -10,6 +10,7 @@
 namespace OxidEsales\GraphQL\ConfigurationAccess\Tests\Unit\Module\Exception;
 
 use OxidEsales\GraphQL\ConfigurationAccess\Module\Exception\ModuleActivationException;
+use OxidEsales\GraphQL\ConfigurationAccess\Module\Exception\ModuleDeactivationException;
 use PHPUnit\Framework\TestCase;
 
 /**
@@ -17,11 +18,19 @@
  */
 final class ModuleActivationExceptionTest extends TestCase
 {
-    public function testException(): void
+    public function testActivationException(): void
     {
         $exception = new ModuleActivationException();
 
         $this->assertInstanceOf(ModuleActivationException::class, $exception);
         $this->assertSame('An error occurred while activating the module.', $exception->getMessage());
     }
+
+    public function testDeactivationException(): void
+    {
+        $exception = new ModuleDeactivationException();
+
+        $this->assertInstanceOf(ModuleDeactivationException::class, $exception);
+        $this->assertSame('An error occurred while deactivating the module.', $exception->getMessage());
+    }
 }