diff --git a/backend/src/Squidex.Domain.Apps.Core.Model/Contents/IdContentData.cs b/backend/src/Squidex.Domain.Apps.Core.Model/Contents/IdContentData.cs
index 7a800ecb6..3440b2403 100644
--- a/backend/src/Squidex.Domain.Apps.Core.Model/Contents/IdContentData.cs
+++ b/backend/src/Squidex.Domain.Apps.Core.Model/Contents/IdContentData.cs
@@ -7,6 +7,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using Squidex.Infrastructure;
 
 namespace Squidex.Domain.Apps.Core.Contents