diff --git a/capnpc-csharp/Generator/CommonSnippetGen.cs b/capnpc-csharp/Generator/CommonSnippetGen.cs
index ddb9867..56d974e 100644
--- a/capnpc-csharp/Generator/CommonSnippetGen.cs
+++ b/capnpc-csharp/Generator/CommonSnippetGen.cs
@@ -93,5 +93,20 @@ namespace CapnpC.Generator
             LiteralExpression(
                 SyntaxKind.NumericLiteralExpression,
                 Literal($"0x{id:x}UL", id));
+
+        public static FieldDeclarationSyntax MakeTypeIdConst(ulong id, GenNames names) =>
+            FieldDeclaration(
+                VariableDeclaration(
+                    IdentifierName("UInt64"))
+                .WithVariables(
+                    SingletonSeparatedList<VariableDeclaratorSyntax>(
+                        VariableDeclarator(names.TypeIdField.Identifier)
+                        .WithInitializer(
+                            EqualsValueClause(HexLiteral(id))))))
+                .WithModifiers(
+                    TokenList(
+                        new[]{
+                            Token(SyntaxKind.PublicKeyword),
+                            Token(SyntaxKind.ConstKeyword)}));
     }
 }
diff --git a/capnpc-csharp/Generator/GenNames.cs b/capnpc-csharp/Generator/GenNames.cs
index f842413..e4620d0 100644
--- a/capnpc-csharp/Generator/GenNames.cs
+++ b/capnpc-csharp/Generator/GenNames.cs
@@ -63,6 +63,7 @@ namespace CapnpC.Generator
         public string MemberAccessPathNameFormat { get; }
         public Name TaskParameter { get; }
         public Name EagerMethod { get; }
+        public Name TypeIdField { get; }
 
         public GenNames(GeneratorOptions options)
         {
@@ -98,6 +99,7 @@ namespace CapnpC.Generator
             MemberAccessPathNameFormat = options.MemberAccessPathNameFormat;
             TaskParameter = new Name(options.TaskParameterName);
             EagerMethod = new Name(options.EagerMethodName);
+            TypeIdField = new Name(options.TypeIdFieldName);
         }
 
         public Name MakeTypeName(TypeDefinition def, NameUsage usage = NameUsage.Default)
diff --git a/capnpc-csharp/Generator/GeneratorOptions.cs b/capnpc-csharp/Generator/GeneratorOptions.cs
index 76faf93..58a0d80 100644
--- a/capnpc-csharp/Generator/GeneratorOptions.cs
+++ b/capnpc-csharp/Generator/GeneratorOptions.cs
@@ -38,5 +38,6 @@ namespace CapnpC.Generator
         public string MemberAccessPathNameFormat { get; set; } = "Path_{0}_{1}";
         public string TaskParameterName { get; set; } = "task";
         public string EagerMethodName { get; set; } = "Eager";
+        public string TypeIdFieldName { get; set; } = "TypeId";
     }
 }