diff --git a/src/testlib/qtestlog.cpp b/src/testlib/qtestlog.cpp
index a20082b6304..f7b75d55021 100644
--- a/src/testlib/qtestlog.cpp
+++ b/src/testlib/qtestlog.cpp
@@ -24,6 +24,7 @@
 #include <QtCore/qbytearray.h>
 #include <QtCore/qelapsedtimer.h>
 #include <QtCore/qlist.h>
+#include <QtCore/qmutex.h>
 #include <QtCore/qvariant.h>
 #if QT_CONFIG(regularexpression)
 #include <QtCore/QRegularExpression>
@@ -138,6 +139,7 @@ namespace QTest {
     };
 
     static IgnoreResultList *ignoreResultList = nullptr;
+    Q_CONSTINIT static QBasicMutex mutex;
 
     static std::vector<QVariant> failOnWarningList;
 
@@ -151,6 +153,8 @@ namespace QTest {
 
     static bool handleIgnoredMessage(QtMsgType type, const QString &message)
     {
+        const QMutexLocker mutexLocker(&QTest::mutex);
+
         if (!ignoreResultList)
             return false;
         IgnoreResultList *last = nullptr;
@@ -270,6 +274,7 @@ void QTestLog::enterTestData(QTestData *data)
 
 int QTestLog::unhandledIgnoreMessages()
 {
+    const QMutexLocker mutexLocker(&QTest::mutex);
     int i = 0;
     QTest::IgnoreResultList *list = QTest::ignoreResultList;
     while (list) {
@@ -290,6 +295,7 @@ void QTestLog::leaveTestFunction()
 
 void QTestLog::printUnhandledIgnoreMessages()
 {
+    const QMutexLocker mutexLocker(&QTest::mutex);
     QString message;
     QTest::IgnoreResultList *list = QTest::ignoreResultList;
     while (list) {
@@ -310,6 +316,7 @@ void QTestLog::printUnhandledIgnoreMessages()
 
 void QTestLog::clearIgnoreMessages()
 {
+    const QMutexLocker mutexLocker(&QTest::mutex);
     QTest::IgnoreResultList::clearList(QTest::ignoreResultList);
 }
 
@@ -594,6 +601,7 @@ void QTestLog::ignoreMessage(QtMsgType type, const char *msg)
 {
     QTEST_ASSERT(msg);
 
+    const QMutexLocker mutexLocker(&QTest::mutex);
     QTest::IgnoreResultList::append(QTest::ignoreResultList, type, QString::fromUtf8(msg));
 }
 
@@ -602,6 +610,7 @@ void QTestLog::ignoreMessage(QtMsgType type, const QRegularExpression &expressio
 {
     QTEST_ASSERT(expression.isValid());
 
+    const QMutexLocker mutexLocker(&QTest::mutex);
     QTest::IgnoreResultList::append(QTest::ignoreResultList, type, QVariant(expression));
 }
 #endif // QT_CONFIG(regularexpression)