diff --git a/comtypes/test/test_typeinfo.py b/comtypes/test/test_typeinfo.py
index 7be16de9..76f25bbb 100644
--- a/comtypes/test/test_typeinfo.py
+++ b/comtypes/test/test_typeinfo.py
@@ -2,13 +2,11 @@
 import os
 import sys
 import unittest
+from _ctypes import COMError
 from ctypes.wintypes import MAX_PATH
 
-import comtypes.hresult
-from comtypes import GUID, COMError
+from comtypes import GUID, hresult, typeinfo
 from comtypes.typeinfo import (
-    TKIND_DISPATCH,
-    TKIND_INTERFACE,
     GetModuleFileName,
     LoadRegTypeLib,
     LoadTypeLibEx,
@@ -69,7 +67,7 @@ def test_TypeInfo(self):
             c_tlib, c_index = ti.GetContainingTypeLib()
             self.assert_tlibattr_equal(c_tlib, tlib)
             self.assertEqual(c_index, index)
-            if ta.typekind in (TKIND_INTERFACE, TKIND_DISPATCH):
+            if ta.typekind in (typeinfo.TKIND_INTERFACE, typeinfo.TKIND_DISPATCH):
                 if ta.cImplTypes:
                     href = ti.GetRefTypeOfImplType(0)
                     base = ti.GetRefTypeInfo(href)
@@ -87,7 +85,7 @@ def test_TypeInfo(self):
         guid_null = GUID()
         with self.assertRaises(COMError) as cm:
             tlib.GetTypeInfoOfGuid(guid_null)
-        self.assertEqual(comtypes.hresult.TYPE_E_ELEMENTNOTFOUND, cm.exception.hresult)
+        self.assertEqual(hresult.TYPE_E_ELEMENTNOTFOUND, cm.exception.hresult)
 
         IID_IFile = GUID("{C7C3F5A4-88A3-11D0-ABCB-00A0C90FFFC0}")
         ti = tlib.GetTypeInfoOfGuid(IID_IFile)
@@ -97,6 +95,42 @@ def test_TypeInfo(self):
         self.assertEqual(c_ti, ti)
         self.assertEqual(IID_IFile, ti.GetTypeAttr().guid)
 
+    def test_pure_dispatch_ITypeInfo(self):
+        tlib = LoadTypeLibEx("msi.dll")
+        IID_Installer = GUID("{000C1090-0000-0000-C000-000000000046}")
+        ti = tlib.GetTypeInfoOfGuid(IID_Installer)
+        ta = ti.GetTypeAttr()
+        self.assertEqual(ta.typekind, typeinfo.TKIND_DISPATCH)
+        with self.assertRaises(COMError) as cm:
+            ti.GetRefTypeOfImplType(-1)
+        self.assertEqual(hresult.TYPE_E_ELEMENTNOTFOUND, cm.exception.hresult)
+        self.assertFalse(ti.GetTypeAttr().wTypeFlags & typeinfo.TYPEFLAG_FDUAL)
+
+    def test_custom_interface_ITypeInfo(self):
+        tlib = LoadTypeLibEx("UIAutomationCore.dll")
+        IID_IUIAutomation = GUID("{30CBE57D-D9D0-452A-AB13-7AC5AC4825EE}")
+        ti = tlib.GetTypeInfoOfGuid(IID_IUIAutomation)
+        ta = ti.GetTypeAttr()
+        self.assertEqual(ta.typekind, typeinfo.TKIND_INTERFACE)
+        with self.assertRaises(COMError) as cm:
+            ti.GetRefTypeOfImplType(-1)
+        self.assertEqual(hresult.TYPE_E_ELEMENTNOTFOUND, cm.exception.hresult)
+        self.assertFalse(ti.GetTypeAttr().wTypeFlags & typeinfo.TYPEFLAG_FDUAL)
+
+    def test_dual_interface_ITypeInfo(self):
+        tlib = LoadTypeLibEx("scrrun.dll")
+        IID_IDictionary = GUID("{42C642C1-97E1-11CF-978F-00A02463E06F}")
+        ti = tlib.GetTypeInfoOfGuid(IID_IDictionary)
+        ta = ti.GetTypeAttr()
+        self.assertEqual(ta.typekind, typeinfo.TKIND_DISPATCH)
+        self.assertTrue(ta.wTypeFlags & typeinfo.TYPEFLAG_FDUAL)
+        refti = ti.GetRefTypeInfo(ti.GetRefTypeOfImplType(-1))
+        refta = refti.GetTypeAttr()
+        self.assertEqual(IID_IDictionary, refti.GetTypeAttr().guid)
+        self.assertTrue(refta.wTypeFlags & typeinfo.TYPEFLAG_FDUAL)
+        self.assertEqual(refta.typekind, typeinfo.TKIND_INTERFACE)
+        self.assertEqual(ti, refti.GetRefTypeInfo(refti.GetRefTypeOfImplType(-1)))
+
 
 class Test_GetModuleFileName(unittest.TestCase):
     @unittest.skipUnless(
diff --git a/comtypes/tools/tlbparser.py b/comtypes/tools/tlbparser.py
index ef400bb8..cad940d7 100644
--- a/comtypes/tools/tlbparser.py
+++ b/comtypes/tools/tlbparser.py
@@ -624,6 +624,7 @@ def parse_typeinfo(self, tinfo: typeinfo.ITypeInfo) -> Any:
             try:
                 # GetRefTypeOfImplType(-1) returns the custom portion
                 # of a dispinterface, if it is dual
+                # See https://learn.microsoft.com/en-us/windows/win32/api/oaidl/nf-oaidl-itypeinfo-getreftypeofimpltype#remarks
                 href = tinfo.GetRefTypeOfImplType(-1)
             except COMError:
                 # no dual interface