diff --git a/Source/Engine/Tests/TestMath.cs b/Source/Engine/Tests/TestMath.cs
index bc1bc1a8d..b8eda936b 100644
--- a/Source/Engine/Tests/TestMath.cs
+++ b/Source/Engine/Tests/TestMath.cs
@@ -1,6 +1,7 @@
 // Copyright (c) 2012-2023 Wojciech Figat. All rights reserved.
 
 #if FLAX_TESTS
+using System;
 using NUnit.Framework;
 
 namespace FlaxEngine.Tests