diff --git a/Perspex.Base/Collections/IReadOnlyPerspexList.cs b/Perspex.Base/Collections/IReadOnlyPerspexList.cs
index 78b7e7392e..7329082f9f 100644
--- a/Perspex.Base/Collections/IReadOnlyPerspexList.cs
+++ b/Perspex.Base/Collections/IReadOnlyPerspexList.cs
@@ -10,7 +10,7 @@ namespace Perspex.Collections
     using System.Collections.Specialized;
     using System.ComponentModel;
 
-    public interface IReadOnlyPerspexList<T> : IReadOnlyList<T>, INotifyCollectionChanged, INotifyPropertyChanged
+    public interface IReadOnlyPerspexList<out T> : IReadOnlyList<T>, INotifyCollectionChanged, INotifyPropertyChanged
     {
     }
 }
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