diff --git a/src/corelib/global/qglobal.h b/src/corelib/global/qglobal.h
index 2464db7c5f5..b85b008f70b 100644
--- a/src/corelib/global/qglobal.h
+++ b/src/corelib/global/qglobal.h
@@ -472,7 +472,7 @@ using qsizetype = QIntegerForSizeof<std::size_t>::Signed;
 #  define QT_ASCII_CAST_WARN
 #endif
 
-#if defined(__i386__) || defined(_WIN32)
+#ifdef Q_PROCESSOR_X86_32
 #  if defined(Q_CC_GNU)
 #    define QT_FASTCALL __attribute__((regparm(3)))
 #  elif defined(Q_CC_MSVC)