diff --git a/src/libraries/System.ComponentModel.Primitives/ref/System.ComponentModel.Primitives.cs b/src/libraries/System.ComponentModel.Primitives/ref/System.ComponentModel.Primitives.cs
index 326179721c1989..c02213d8371654 100644
--- a/src/libraries/System.ComponentModel.Primitives/ref/System.ComponentModel.Primitives.cs
+++ b/src/libraries/System.ComponentModel.Primitives/ref/System.ComponentModel.Primitives.cs
@@ -231,7 +231,7 @@ public InvalidEnumArgumentException(string? argumentName, int invalidValue, Syst
     public partial interface ISite : System.IServiceProvider
     {
         System.ComponentModel.IComponent Component { get; }
-        System.ComponentModel.IContainer Container { get; }
+        System.ComponentModel.IContainer? Container { get; }
         bool DesignMode { get; }
         string? Name { get; set; }
     }
diff --git a/src/libraries/System.ComponentModel.Primitives/src/System/ComponentModel/ISite.cs b/src/libraries/System.ComponentModel.Primitives/src/System/ComponentModel/ISite.cs
index 3a6f9c244e1c0e..e51287ff1f8675 100644
--- a/src/libraries/System.ComponentModel.Primitives/src/System/ComponentModel/ISite.cs
+++ b/src/libraries/System.ComponentModel.Primitives/src/System/ComponentModel/ISite.cs
@@ -26,7 +26,7 @@ public interface ISite : IServiceProvider
         /// When implemented by a class, gets the container associated with
         /// the <see cref='System.ComponentModel.ISite'/>.
         /// </summary>
-        IContainer Container { get; }
+        IContainer? Container { get; }
 
         /// <summary>
         /// When implemented by a class, determines whether the component is in design mode.