diff --git a/cmake/QtHeadersClean.cmake b/cmake/QtHeadersClean.cmake
index 497c3f2909..b19990eac4 100644
--- a/cmake/QtHeadersClean.cmake
+++ b/cmake/QtHeadersClean.cmake
@@ -181,9 +181,7 @@ function(qt_internal_add_headersclean_target module_target module_headers)
         )
         set(input_header_path_type ABSOLUTE)
     elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
-        # -Za would enable strict standards behavior, but we can't add it because
-        # <windows.h> and <GL.h> violate the standards.
-        set(hcleanFLAGS -std:c++latest -Zc:__cplusplus -WX -W3)
+        set(hcleanFLAGS -std:c++latest -Zc:__cplusplus -Za -WX -W3)
 
         # cl.exe needs a source path
         get_filename_component(source_path "${QT_MKSPECS_DIR}/features/data/dummy.cpp" REALPATH)