diff --git a/ICSharpCode.Decompiler.Tests/TestCases/Pretty/Issue3909.cs b/ICSharpCode.Decompiler.Tests/TestCases/Pretty/Issue3909.cs
index 5bc5a4b75..8d8284974 100644
--- a/ICSharpCode.Decompiler.Tests/TestCases/Pretty/Issue3909.cs
+++ b/ICSharpCode.Decompiler.Tests/TestCases/Pretty/Issue3909.cs
@@ -222,5 +222,28 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 				return null;
 			}
 		}
+#if CS130
+		public class BaseWithAllowsRefStruct
+		{
+			public virtual void Annotated<T>(T? value) where T : allows ref struct
+			{
+			}
+
+			public virtual void Plain<T>(T value) where T : allows ref struct
+			{
+			}
+		}
+
+		public class DerivedWithAllowsRefStruct : BaseWithAllowsRefStruct
+		{
+			public override void Annotated<T>(T? value) where T : default
+			{
+			}
+
+			public override void Plain<T>(T value)
+			{
+			}
+		}
+#endif
 	}
 }
diff --git a/ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs b/ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs
index dc2d2f955..a1e99ea6c 100644
--- a/ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs
+++ b/ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs
@@ -2619,6 +2619,9 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		// metadata, so which disambiguator is legal follows from them without resolving the base
 		// member. The restated disambiguator leaves no metadata trace of its own, hence it must be
 		// derived rather than read back.
+		// The clause is built here rather than through ConvertTypeParameterConstraint, which also
+		// prints 'allows ref struct' from the byreflike flag. That flag is re-emitted on the
+		// override's own type parameter as well, and restating it is CS0460.
 		void AddNullabilityDisambiguatingConstraints(MethodDeclaration decl, IMethod method)
 		{
 			if (method.TypeParameters.Count == 0)