diff --git a/src/corelib/statemachine/qstatemachine.cpp b/src/corelib/statemachine/qstatemachine.cpp
index 59b6b55494..ec4f3dea4c 100644
--- a/src/corelib/statemachine/qstatemachine.cpp
+++ b/src/corelib/statemachine/qstatemachine.cpp
@@ -1703,8 +1703,10 @@ void QStateMachinePrivate::unregisterTransition(QAbstractTransition *transition)
 void QStateMachinePrivate::maybeRegisterSignalTransition(QSignalTransition *transition)
 {
     Q_Q(QStateMachine);
-    if ((state == Running) && configuration.contains(transition->sourceState()))
+    if (((state == Running) && configuration.contains(transition->sourceState()))
+            || (transition->senderObject() && (transition->senderObject()->thread() != q->thread()))) {
         registerSignalTransition(transition);
+    }
 }
 
 void QStateMachinePrivate::registerSignalTransition(QSignalTransition *transition)
@@ -1766,11 +1768,15 @@ void QStateMachinePrivate::registerSignalTransition(QSignalTransition *transitio
 
 void QStateMachinePrivate::unregisterSignalTransition(QSignalTransition *transition)
 {
+    Q_Q(QStateMachine);
     int signalIndex = QSignalTransitionPrivate::get(transition)->signalIndex;
     if (signalIndex == -1)
         return; // not registered
-    QSignalTransitionPrivate::get(transition)->signalIndex = -1;
     const QObject *sender = QSignalTransitionPrivate::get(transition)->sender;
+    // Don't unregister if the sender is on another thread
+    if (!sender || (sender->thread() != q->thread()))
+        return;
+    QSignalTransitionPrivate::get(transition)->signalIndex = -1;
     QVector<int> &connectedSignalIndexes = connections[sender];
     Q_ASSERT(connectedSignalIndexes.size() > signalIndex);
     Q_ASSERT(connectedSignalIndexes.at(signalIndex) != 0);
diff --git a/tests/auto/corelib/statemachine/qstatemachine/tst_qstatemachine.cpp b/tests/auto/corelib/statemachine/qstatemachine/tst_qstatemachine.cpp
index b14ab7d1c5..8c67c0ec03 100644
--- a/tests/auto/corelib/statemachine/qstatemachine/tst_qstatemachine.cpp
+++ b/tests/auto/corelib/statemachine/qstatemachine/tst_qstatemachine.cpp
@@ -208,6 +208,7 @@ private slots:
     void signalTransitionNormalizeSignature();
     void createSignalTransitionWhenRunning();
     void createEventTransitionWhenRunning();
+    void signalTransitionSenderInDifferentThread();
 };
 
 class TestState : public QState
@@ -4827,5 +4828,61 @@ void tst_QStateMachine::createEventTransitionWhenRunning()
     QTRY_VERIFY(machine.configuration().contains(s4));
 }
 
+class SignalEmitterThread : public QThread
+{
+    Q_OBJECT
+public:
+    SignalEmitterThread(QObject *parent = 0)
+        : QThread(parent)
+    {
+        moveToThread(this);
+    }
+
+Q_SIGNALS:
+    void signal1();
+    void signal2();
+
+public Q_SLOTS:
+    void emitSignals()
+    {
+        emit signal1();
+        emit signal2();
+    }
+};
+
+// QTBUG-19789
+void tst_QStateMachine::signalTransitionSenderInDifferentThread()
+{
+    QStateMachine machine;
+    QState *s1 = new QState(&machine);
+    machine.setInitialState(s1);
+
+    SignalEmitterThread thread;
+    QState *s2 = new QState(&machine);
+    s1->addTransition(&thread, SIGNAL(signal1()), s2);
+
+    QFinalState *s3 = new QFinalState(&machine);
+    s2->addTransition(&thread, SIGNAL(signal2()), s3);
+
+    thread.start();
+    QTRY_VERIFY(thread.isRunning());
+
+    machine.start();
+    QTRY_VERIFY(machine.configuration().contains(s1));
+
+    QMetaObject::invokeMethod(&thread, "emitSignals");
+    // thread emits both signal1() and signal2(), so we should end in s3
+    QTRY_VERIFY(machine.configuration().contains(s3));
+
+    // Run the machine again; transitions should still be registered
+    machine.start();
+    QTRY_VERIFY(machine.configuration().contains(s1));
+    QMetaObject::invokeMethod(&thread, "emitSignals");
+    QTRY_VERIFY(machine.configuration().contains(s3));
+
+    thread.quit();
+    QTRY_VERIFY(thread.wait());
+}
+
 QTEST_MAIN(tst_QStateMachine)
 #include "tst_qstatemachine.moc"