diff --git a/nukebuild/RefAssemblyGenerator.cs b/nukebuild/RefAssemblyGenerator.cs
index f103f169196..f8d03b0232b 100644
--- a/nukebuild/RefAssemblyGenerator.cs
+++ b/nukebuild/RefAssemblyGenerator.cs
@@ -84,6 +84,7 @@ static void ProcessType(TypeDefinition type, MethodReference obsoleteCtor)
             type.Methods.Add(new MethodDefinition(
                 "(This interface or abstract class is -not- implementable by user code !)",
                 MethodAttributes.Assembly
+                | MethodAttributes.Virtual
                 | MethodAttributes.Abstract
                 | MethodAttributes.NewSlot
                 | MethodAttributes.HideBySig, type.Module.TypeSystem.Void));