diff --git a/src/Framework/Framework/Compilation/CompiledAssemblyCache.cs b/src/Framework/Framework/Compilation/CompiledAssemblyCache.cs
index b8a990dce4..8aea8818ed 100644
--- a/src/Framework/Framework/Compilation/CompiledAssemblyCache.cs
+++ b/src/Framework/Framework/Compilation/CompiledAssemblyCache.cs
@@ -172,12 +172,13 @@ private HashSet<string> GetAllNamespaces()
             foreach (var a in GetAllAssemblies())
             {
                 string? lastNs = null; // namespaces come in batches, usually, so no need to hash it everytime when a quick compare says it's the same as last time
-                foreach (var type in a.ExportedTypes)
+                foreach (var type in a.GetLoadableTypes())
                 {
                     var ns = type.Namespace;
                     if (ns is null || lastNs == ns)
                         continue;
-                    result.Add(ns);                   
+                    result.Add(ns);
+                    lastNs = ns;
                 }
             }
             return result;
diff --git a/src/Tests/Runtime/ControlTree/DefaultControlTreeResolver/ImportDirectiveTests.cs b/src/Tests/Runtime/ControlTree/DefaultControlTreeResolver/ImportDirectiveTests.cs
index acd28c81bf..d53853e6ac 100644
--- a/src/Tests/Runtime/ControlTree/DefaultControlTreeResolver/ImportDirectiveTests.cs
+++ b/src/Tests/Runtime/ControlTree/DefaultControlTreeResolver/ImportDirectiveTests.cs
@@ -5,6 +5,11 @@
 using System;
 using System.Collections.Generic;
 
+namespace DotVVM.Framework.Tests.Runtime.ControlTree.TestInternalOnlyNamespace
+{
+    class InternalClass { }
+}
+
 namespace DotVVM.Framework.Tests.Runtime.ControlTree
 {
     [TestClass]
@@ -70,6 +75,46 @@ @viewModel object
             Assert.AreEqual(typeof(List<int>).FullName, importDirective.Type.FullName);
         }
 
+        [TestMethod]
+        public void ResolvedTree_ImportDirective_NamespaceDoesNotExist()
+        {
+            var root = ParseSource(@"
+@viewModel object
+@import This.Namespace.Does.Not.Exist
+");
+            var importDirective = EnsureSingleResolvedImportDirective(root);
+
+            Assert.IsTrue(importDirective.HasError);
+            Assert.AreEqual("This.Namespace.Does.Not.Exist is unknown type or namespace.", importDirective.DothtmlNode.NodeErrors.Single());
+        }
+        [TestMethod]
+        public void ResolvedTree_ImportDirective_NamespaceDoesNotExist_Alias()
+        {
+            var root = ParseSource(@"
+@viewModel object
+@import testns = This.Namespace.Does.Not.Exist
+");
+            var importDirective = EnsureSingleResolvedImportDirective(root);
+
+            Assert.IsTrue(importDirective.HasError);
+            Assert.AreEqual("This.Namespace.Does.Not.Exist is unknown type or namespace.", importDirective.DothtmlNode.NodeErrors.Single());
+        }
+
+        [TestMethod]
+        public void ResolvedTree_ImportDirective_InternalNamespace()
+        {
+            var root = ParseSource(@"
+@viewModel object
+@import DotVVM.Framework.Tests.Runtime.ControlTree.TestInternalOnlyNamespace
+");
+            var importDirective = EnsureSingleResolvedImportDirective(root);
+
+            Assert.IsFalse(importDirective.HasError, message: importDirective.DothtmlNode.NodeErrors.SingleOrDefault());
+            Assert.IsNull(importDirective.Type);
+            Assert.IsTrue(importDirective.IsNamespace);
+        }
+
+
         private static ResolvedImportDirective EnsureSingleResolvedImportDirective(ResolvedTreeRoot root) =>
                 root.Directives["import"]
                     .Single()