diff --git a/src/corelib/global/qglobal.cpp b/src/corelib/global/qglobal.cpp
index 738e39658fe..c894471ad63 100644
--- a/src/corelib/global/qglobal.cpp
+++ b/src/corelib/global/qglobal.cpp
@@ -2977,7 +2977,8 @@ QByteArray QSysInfo::machineUniqueId()
 {
 #if defined(Q_OS_DARWIN) && __has_include(<IOKit/IOKitLib.h>)
     char uuid[UuidStringLen + 1];
-    io_service_t service = IOServiceGetMatchingService(kIOMasterPortDefault, IOServiceMatching("IOPlatformExpertDevice"));
+    static const mach_port_t defaultPort = 0; // Effectively kIOMasterPortDefault/kIOMainPortDefault
+    io_service_t service = IOServiceGetMatchingService(defaultPort, IOServiceMatching("IOPlatformExpertDevice"));
     QCFString stringRef = (CFStringRef)IORegistryEntryCreateCFProperty(service, CFSTR(kIOPlatformUUIDKey), kCFAllocatorDefault, 0);
     CFStringGetCString(stringRef, uuid, sizeof(uuid), kCFStringEncodingMacRoman);
     return QByteArray(uuid);