diff --git a/src/corelib/text/qlocale.cpp b/src/corelib/text/qlocale.cpp
index 8c0ce2434e..50e2b352f4 100644
--- a/src/corelib/text/qlocale.cpp
+++ b/src/corelib/text/qlocale.cpp
@@ -2640,15 +2640,15 @@ QList<QLocale> QLocale::matchingLocales(QLocale::Language language, QLocale::Scr
         result.reserve(locale_data_size);
 
     quint16 index = locale_index[language];
-    Q_ASSERT(filter.acceptLanguage(locale_data[index].m_language_id));
-    do {
+    // There may be no matches, for some languages (e.g. Abkhazian at CLDR v39).
+    while (filter.acceptLanguage(locale_data[index].m_language_id)) {
         const QLocaleId id = locale_data[index].id();
         if (filter.acceptScriptTerritory(id)) {
             result.append(QLocale(*(id.language_id == C ? c_private()
                                     : new QLocalePrivate(locale_data + index, index))));
         }
         ++index;
-    } while (filter.acceptLanguage(locale_data[index].m_language_id));
+    }
 
     return result;
 }
diff --git a/tests/auto/corelib/text/qlocale/tst_qlocale.cpp b/tests/auto/corelib/text/qlocale/tst_qlocale.cpp
index 56eef7ac99..785bfdef44 100644
--- a/tests/auto/corelib/text/qlocale/tst_qlocale.cpp
+++ b/tests/auto/corelib/text/qlocale/tst_qlocale.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 test suite of the Qt Toolkit.
@@ -716,6 +716,12 @@ void tst_QLocale::matchingLocales()
     QVERIFY(!locales.isEmpty());
     QVERIFY(!locales.contains(c));
     QVERIFY(locales.contains(ru_RU));
+
+    // Regression check for assertion failure when no locales match:
+    locales = QLocale::matchingLocales(QLocale::Abkhazian, QLocale::AnyScript, QLocale::AnyTerritory);
+    // Empty in CLDR v39, but don't require that.
+    QVERIFY(!locales.contains(c));
+    QVERIFY(!locales.contains(ru_RU));
 }
 
 void tst_QLocale::unixLocaleName_data()