diff --git a/cmake/QtMkspecHelpers.cmake b/cmake/QtMkspecHelpers.cmake
index cd08daa2c44..a9612966b5f 100644
--- a/cmake/QtMkspecHelpers.cmake
+++ b/cmake/QtMkspecHelpers.cmake
@@ -33,11 +33,13 @@ macro(qt_internal_setup_platform_definitions_and_mkspec)
                 set(QT_DEFAULT_MKSPEC win32-clang-g++)
             endif()
         elseif(MSVC)
-            if(CMAKE_SYSTEM_PROCESSOR STREQUAL "arm64")
+            string(TOLOWER "${CMAKE_SYSTEM_PROCESSOR}" cmake_system_processor_case_independent)
+            if(cmake_system_processor_case_independent STREQUAL "arm64")
                 set(QT_DEFAULT_MKSPEC win32-arm64-msvc)
             else()
                 set(QT_DEFAULT_MKSPEC win32-msvc)
             endif()
+            unset(cmake_system_processor_case_independent)
         elseif(MINGW)
             set(QT_DEFAULT_MKSPEC win32-g++)
             list(APPEND QT_DEFAULT_PLATFORM_DEFINITIONS MINGW_HAS_SECURE_API=1)