diff --git a/tests/GameCult.Geometry.Tests/GeometryDocumentTests.cs b/tests/GameCult.Geometry.Tests/GeometryDocumentTests.cs
index 2576c295..b5f63775 100644
--- a/tests/GameCult.Geometry.Tests/GeometryDocumentTests.cs
+++ b/tests/GameCult.Geometry.Tests/GeometryDocumentTests.cs
@@ -10,6 +10,7 @@ using R3;
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 using System.Text.Json;
 using System.Threading.Tasks;