diff --git a/Source/cmQtAutoGenInitializer.cxx b/Source/cmQtAutoGenInitializer.cxx
index d4819a307d..9dfd9dbc0d 100644
--- a/Source/cmQtAutoGenInitializer.cxx
+++ b/Source/cmQtAutoGenInitializer.cxx
@@ -489,10 +489,13 @@ bool cmQtAutoGenInitializer::InitMoc()
 
   // Moc includes
   {
-    bool const appendImplicit = (this->QtVersion.Major == 5);
+    // We need to disable this until we have all implicit includes available.
+    // See issue #18669.
+    // bool const appendImplicit = (this->QtVersion.Major == 5);
+
     auto GetIncludeDirs =
-      [this, localGen,
-       appendImplicit](std::string const& cfg) -> std::vector<std::string> {
+      [this, localGen](std::string const& cfg) -> std::vector<std::string> {
+      bool const appendImplicit = false;
       // Get the include dirs for this target, without stripping the implicit
       // include dirs off, see
       // https://gitlab.kitware.com/cmake/cmake/issues/13667
diff --git a/Tests/QtAutogen/Tests.cmake b/Tests/QtAutogen/Tests.cmake
index 096d5e3bd5..c53fb4f1d8 100644
--- a/Tests/QtAutogen/Tests.cmake
+++ b/Tests/QtAutogen/Tests.cmake
@@ -39,7 +39,8 @@ endif()
 # Qt5 only tests
 if(QT_TEST_VERSION GREATER 4)
   ADD_AUTOGEN_TEST(MocMacroName mocMacroName)
-  ADD_AUTOGEN_TEST(MocOsMacros)
+  # Disabled for issue #18669
+  #ADD_AUTOGEN_TEST(MocOsMacros)
   ADD_AUTOGEN_TEST(RerunMocPlugin)
   if(APPLE)
     ADD_AUTOGEN_TEST(MacOsFW)