diff --git a/src/scripttools/debugging/qscriptdebuggerbackend.cpp b/src/scripttools/debugging/qscriptdebuggerbackend.cpp
index 1da004419..4a7b453d9 100644
--- a/src/scripttools/debugging/qscriptdebuggerbackend.cpp
+++ b/src/scripttools/debugging/qscriptdebuggerbackend.cpp
@@ -154,6 +154,7 @@ void QScriptDebuggerBackendPrivate::postEvent(QEvent *e)
 {
     if (!eventReceiver) {
         eventReceiver = new QScriptDebuggerBackendEventReceiver(this);
+        Q_ASSERT(agent != 0);
         eventReceiver->moveToThread(agent->engine()->thread());
     }
     QCoreApplication::postEvent(eventReceiver, e);
diff --git a/src/scripttools/debugging/qscriptenginedebuggerfrontend.cpp b/src/scripttools/debugging/qscriptenginedebuggerfrontend.cpp
index 611a6f35c..9d13b2736 100644
--- a/src/scripttools/debugging/qscriptenginedebuggerfrontend.cpp
+++ b/src/scripttools/debugging/qscriptenginedebuggerfrontend.cpp
@@ -201,7 +201,8 @@ QScriptEngineDebuggerBackend::~QScriptEngineDebuggerBackend()
 void QScriptEngineDebuggerBackend::processCommand(int id, const QScriptDebuggerCommand &command)
 {
     Q_D(QScriptEngineDebuggerBackend);
-    d->postEvent(new QScriptDebuggerCommandEvent(id, command));
+    if (d->agent)
+        d->postEvent(new QScriptDebuggerCommandEvent(id, command));
 }
 
 /*!