diff --git a/capnpc-csharp/Model/Annotation.cs b/capnpc-csharp/Model/Annotation.cs
index 6dbbd9a..1f5a9c0 100644
--- a/capnpc-csharp/Model/Annotation.cs
+++ b/capnpc-csharp/Model/Annotation.cs
@@ -1,4 +1,5 @@
-
+using System.Diagnostics;
+
 namespace CapnpC.Model
 {
     class Annotation : IDefinition
@@ -11,6 +12,7 @@ namespace CapnpC.Model
 
         public Annotation(ulong id, IHasNestedDefinitions parent)
         {
+            Trace.Assert(parent != null);
             Id = id;
             DeclaringElement = parent;
             parent.NestedDefinitions.Add(this);
diff --git a/capnpc-csharp/Model/Constant.cs b/capnpc-csharp/Model/Constant.cs
index a992ca0..64e9107 100644
--- a/capnpc-csharp/Model/Constant.cs
+++ b/capnpc-csharp/Model/Constant.cs
@@ -1,4 +1,5 @@
-
+using System.Diagnostics;
+
 namespace CapnpC.Model
 {
     class Constant : IDefinition
@@ -11,6 +12,7 @@ namespace CapnpC.Model
 
         public Constant(ulong id, IHasNestedDefinitions parent)
         {
+            Trace.Assert(parent != null);
             Id = id;
             DeclaringElement = parent;
             parent.NestedDefinitions.Add(this);
diff --git a/capnpc-csharp/Model/GenFile.cs b/capnpc-csharp/Model/GenFile.cs
index f912303..15b7918 100644
--- a/capnpc-csharp/Model/GenFile.cs
+++ b/capnpc-csharp/Model/GenFile.cs
@@ -6,7 +6,7 @@ namespace CapnpC.Model
     {
         public ulong Id { get;  }
         public TypeTag Tag { get => TypeTag.File;  }
-        public IHasNestedDefinitions DeclaringElement { get; }
+        public IHasNestedDefinitions DeclaringElement { get => null; }
 
         public string Name { get; set; }
         public string[] Namespace { get; set; }
diff --git a/capnpc-csharp/Model/SchemaModel.cs b/capnpc-csharp/Model/SchemaModel.cs
index 4ebafec..4aca4f7 100644
--- a/capnpc-csharp/Model/SchemaModel.cs
+++ b/capnpc-csharp/Model/SchemaModel.cs
@@ -137,6 +137,7 @@ namespace CapnpC.Model
 
             if (def == null)
             {
+                Trace.Assert(state.parent != null, $"The {node.GetTypeTag().ToString()} node {node.StrId()} was expected to have a parent.");
                 var typeDef = _typeDefMgr.CreateTypeDef(id, node.GetTypeTag(), state.parent);
                 typeDef.Name = name;
                 def = typeDef;
diff --git a/capnpc-csharp/Model/TypeDefinition.cs b/capnpc-csharp/Model/TypeDefinition.cs
index 910d4bd..19fb166 100644
--- a/capnpc-csharp/Model/TypeDefinition.cs
+++ b/capnpc-csharp/Model/TypeDefinition.cs
@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Linq;
 namespace CapnpC.Model
 {
@@ -18,6 +19,7 @@ namespace CapnpC.Model
 
         public TypeDefinition(TypeTag tag, ulong id, IHasNestedDefinitions parent)
         {
+            Trace.Assert(parent != null);
             Tag = tag;
             Id = id;
             DeclaringElement = parent;