diff --git a/src/testlib/qjunittestlogger.cpp b/src/testlib/qjunittestlogger.cpp
index 2ba6e71bb98..ef4f1561c15 100644
--- a/src/testlib/qjunittestlogger.cpp
+++ b/src/testlib/qjunittestlogger.cpp
@@ -130,14 +130,17 @@ void QJUnitTestLogger::enterTestFunction(const char *function)
 
 void QJUnitTestLogger::enterTestCase(const char *name)
 {
-    currentTestCase = new QTestElement(QTest::LET_TestCase);
-    currentTestCase->addAttribute(QTest::AI_Name, name);
-    currentTestCase->addAttribute(QTest::AI_Classname, QTestResult::currentTestObjectName());
-    listOfTestcases.push_back(currentTestCase);
+    {
+        QMutexLocker locker(&mutex);
+        currentTestCase = new QTestElement(QTest::LET_TestCase);
+        currentTestCase->addAttribute(QTest::AI_Name, name);
+        currentTestCase->addAttribute(QTest::AI_Classname, QTestResult::currentTestObjectName());
+        listOfTestcases.push_back(currentTestCase);
 
-    Q_ASSERT(!systemOutputElement && !systemErrorElement);
-    systemOutputElement = new QTestElement(QTest::LET_SystemOutput);
-    systemErrorElement = new QTestElement(QTest::LET_SystemError);
+        Q_ASSERT(!systemOutputElement && !systemErrorElement);
+        systemOutputElement = new QTestElement(QTest::LET_SystemOutput);
+        systemErrorElement = new QTestElement(QTest::LET_SystemError);
+    }
 
     // The element will be deleted when the suite is deleted
 
@@ -174,6 +177,7 @@ void QJUnitTestLogger::leaveTestFunction()
 
 void QJUnitTestLogger::leaveTestCase()
 {
+    QMutexLocker locker(&mutex);
     currentTestCase->addAttribute(QTest::AI_Time,
         toSecondsFormat(elapsedTestCaseSeconds() * 1000).constData());
 
@@ -257,6 +261,7 @@ void QJUnitTestLogger::addMessage(MessageTypes type, const QString &message, con
     Q_UNUSED(file);
     Q_UNUSED(line);
 
+    QMutexLocker locker(&mutex);
     if (type == QFatal) {
         addFailure(QTest::LET_Error, "qfatal", message);
         return;
diff --git a/src/testlib/qjunittestlogger_p.h b/src/testlib/qjunittestlogger_p.h
index 6a7ff316152..6c4c7d71f2a 100644
--- a/src/testlib/qjunittestlogger_p.h
+++ b/src/testlib/qjunittestlogger_p.h
@@ -19,6 +19,7 @@
 
 #include <QtTest/private/qabstracttestlogger_p.h>
 #include <QtTest/private/qtestelementattribute_p.h>
+#include <QtCore/qmutex.h>
 
 #include <vector>
 
@@ -61,6 +62,9 @@ class QJUnitTestLogger : public QAbstractTestLogger
         QTestElement *systemOutputElement = nullptr;
         QTestElement *systemErrorElement = nullptr;
         QTestJUnitStreamer *logFormatter = nullptr;
+        // protects currentTestCase, systemOutputElement and systemErrorElement
+        // in case of qDebug()/qWarning() etc. from threads
+        QMutex mutex;
 
         int testCounter = 0;
         int failureCounter = 0;