diff --git a/src/dscom.demo/assembly5/ExplodeyBaseClass.cs b/src/dscom.demo/assembly5/ExplodeyBaseClass.cs
index 1b7e75b..fa15457 100644
--- a/src/dscom.demo/assembly5/ExplodeyBaseClass.cs
+++ b/src/dscom.demo/assembly5/ExplodeyBaseClass.cs
@@ -4,4 +4,8 @@ namespace dSPACE.Runtime.InteropServices.DemoAssembly5;
 
 public class ExplodeyBaseClass : UserControl
 {
+    private sealed class PrivateImplementationDetails
+    {
+        // required to reproduce #259
+    }
 }
diff --git a/src/dscom/writer/LibraryWriter.cs b/src/dscom/writer/LibraryWriter.cs
index 1044ca8..a6b13ec 100644
--- a/src/dscom/writer/LibraryWriter.cs
+++ b/src/dscom/writer/LibraryWriter.cs
@@ -97,11 +97,6 @@ private void CollectAllTypes()
 
         foreach (var type in types)
         {
-            if (type == null || type.Namespace is null)
-            {
-                continue;
-            }
-
             var comVisibleAttribute = type.GetCustomAttribute<ComVisibleAttribute>();
 
             if (typesAreVisibleForComByDefault && comVisibleAttribute != null && !comVisibleAttribute.Value)
@@ -114,11 +109,17 @@ private void CollectAllTypes()
                 continue;
             }
 
+
             if (!type.IsPublic && !type.IsNestedPublic)
             {
                 continue;
             }
 
+            if (type.Namespace is null)
+            {
+                continue;
+            }
+
             if (type.IsGenericType)
             {
                 continue;