diff --git a/src/libraries/System.Runtime.InteropServices.JavaScript/ref/System.Runtime.InteropServices.JavaScript.cs b/src/libraries/System.Runtime.InteropServices.JavaScript/ref/System.Runtime.InteropServices.JavaScript.cs
index 54b2c5352f8c21..c910e7f8228c5d 100644
--- a/src/libraries/System.Runtime.InteropServices.JavaScript/ref/System.Runtime.InteropServices.JavaScript.cs
+++ b/src/libraries/System.Runtime.InteropServices.JavaScript/ref/System.Runtime.InteropServices.JavaScript.cs
@@ -201,7 +201,9 @@ public sealed class JSMarshalerType
 [System.ComponentModel.EditorBrowsableAttribute(System.ComponentModel.EditorBrowsableState.Never)]
 public struct JSMarshalerArgument
 {
+    [System.ComponentModel.EditorBrowsableAttribute(System.ComponentModel.EditorBrowsableState.Never)]
     public delegate void ArgumentToManagedCallback<T>(ref JSMarshalerArgument arg, out T value);
+    [System.ComponentModel.EditorBrowsableAttribute(System.ComponentModel.EditorBrowsableState.Never)]
     public delegate void ArgumentToJSCallback<T>(ref JSMarshalerArgument arg, T value);
     public void Initialize() { throw null; }
     public void ToManaged(out bool value) { throw null; }
diff --git a/src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Marshaling/JSMarshalerArgument.Task.cs b/src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Marshaling/JSMarshalerArgument.Task.cs
index f3101e881fe9ac..13876867c8a544 100644
--- a/src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Marshaling/JSMarshalerArgument.Task.cs
+++ b/src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Marshaling/JSMarshalerArgument.Task.cs
@@ -13,12 +13,14 @@ public partial struct JSMarshalerArgument
         /// Helps with marshaling of the Task result or Function arguments.
         /// It's used by JSImport code generator and should not be used by developers in source code.
         /// </summary>
+        [System.ComponentModel.EditorBrowsableAttribute(System.ComponentModel.EditorBrowsableState.Never)]
         public delegate void ArgumentToManagedCallback<T>(ref JSMarshalerArgument arg, out T value);
 
         /// <summary>
         /// Helps with marshaling of the Task result or Function arguments.
         /// It's used by JSImport code generator and should not be used by developers in source code.
         /// </summary>
+        [System.ComponentModel.EditorBrowsableAttribute(System.ComponentModel.EditorBrowsableState.Never)]
         public delegate void ArgumentToJSCallback<T>(ref JSMarshalerArgument arg, T value);
 
         /// <summary>