2 files changed, 18 insertions, 14 deletions
diff --git a/src/corelib/statemachine/qsignaltransition.cpp b/src/corelib/statemachine/qsignaltransition.cpp
index 4caa917..9ffcb9c 100644
--- a/src/corelib/statemachine/qsignaltransition.cpp
+++ b/src/corelib/statemachine/qsignaltransition.cpp
@@ -118,19 +118,20 @@ QSignalTransitionPrivate *QSignalTransitionPrivate::get(QSignalTransition *q)
     return q->d_func();
 }
 
-void QSignalTransitionPrivate::invalidate()
+void QSignalTransitionPrivate::unregister()
 {
     Q_Q(QSignalTransition);
-    if (signalIndex != -1) {
-        QState *source = sourceState();
-        QStatePrivate *source_d = QStatePrivate::get(source);
-        QStateMachinePrivate *mach = QStateMachinePrivate::get(source_d->machine());
-        if (mach) {
-            mach->unregisterSignalTransition(q);
-            if (mach->configuration.contains(source))
-                mach->registerSignalTransition(q);
-        }
-    }
+    if ((signalIndex == -1) || !machine())
+        return;
+    QStateMachinePrivate::get(machine())->unregisterSignalTransition(q);
+}
+
+void QSignalTransitionPrivate::maybeRegister()
+{
+    Q_Q(QSignalTransition);
+    if (!machine() || !machine()->configuration().contains(sourceState()))
+        return;
+    QStateMachinePrivate::get(machine())->registerSignalTransition(q);
 }
 
 /*!
@@ -193,8 +194,9 @@ void QSignalTransition::setSenderObject(QObject *sender)
     Q_D(QSignalTransition);
     if (sender == d->sender)
         return;
+    d->unregister();
     d->sender = sender;
-    d->invalidate();
+    d->maybeRegister();
 }
 
 /*!
@@ -214,8 +216,9 @@ void QSignalTransition::setSignal(const QByteArray &signal)
     Q_D(QSignalTransition);
     if (signal == d->signal)
         return;
+    d->unregister();
     d->signal = signal;
-    d->invalidate();
+    d->maybeRegister();
 }
 
 /*!
diff --git a/src/corelib/statemachine/qsignaltransition_p.h b/src/corelib/statemachine/qsignaltransition_p.h
index a23e58c..339de63 100644
--- a/src/corelib/statemachine/qsignaltransition_p.h
+++ b/src/corelib/statemachine/qsignaltransition_p.h
@@ -66,7 +66,8 @@ public:
 
     static QSignalTransitionPrivate *get(QSignalTransition *q);
 
-    void invalidate();
+    void unregister();
+    void maybeRegister();
 
     QObject *sender;
     QByteArray signal;