diff --git a/src/corelib/text/qlocale_unix.cpp b/src/corelib/text/qlocale_unix.cpp
index 29053a7074..8f5624f79e 100644
--- a/src/corelib/text/qlocale_unix.cpp
+++ b/src/corelib/text/qlocale_unix.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2020 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtCore module of the Qt Toolkit.
@@ -77,6 +77,8 @@ void QSystemLocaleData::readEnvironment()
 {
     QWriteLocker locker(&lock);
 
+    // See https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_02
+    // for the semantics of each of these:
     QByteArray all = qgetenv("LC_ALL");
     QByteArray numeric  = all.isEmpty() ? qgetenv("LC_NUMERIC") : all;
     QByteArray time     = all.isEmpty() ? qgetenv("LC_TIME") : all;