diff --git a/src/libs/qmljs/qmljsinterpreter.cpp b/src/libs/qmljs/qmljsinterpreter.cpp
index ff32bb517bf..e23deedbbe0 100644
--- a/src/libs/qmljs/qmljsinterpreter.cpp
+++ b/src/libs/qmljs/qmljsinterpreter.cpp
@@ -2528,6 +2528,7 @@ const ObjectValue *Engine::qtObject() const
 
 void Engine::registerValue(Value *value)
 {
+    QMutexLocker locker(&_mutex);
     _registeredValues.append(value);
 }
 
diff --git a/src/libs/qmljs/qmljsinterpreter.h b/src/libs/qmljs/qmljsinterpreter.h
index f6c7086fb18..771aa729428 100644
--- a/src/libs/qmljs/qmljsinterpreter.h
+++ b/src/libs/qmljs/qmljsinterpreter.h
@@ -40,6 +40,7 @@
 #include <QtCore/QString>
 #include <QtCore/QHash>
 #include <QtCore/QSet>
+#include <QtCore/QMutex>
 
 namespace QmlJS {
 
@@ -735,6 +736,8 @@ private:
     TypeId _typeId;
 
     CppQmlTypes _cppQmlTypes;
+
+    QMutex _mutex;
 };