diff --git a/DestinationGLCanvas.cpp b/DestinationGLCanvas.cpp
index a63750c..ee771a5 100644
--- a/DestinationGLCanvas.cpp
+++ b/DestinationGLCanvas.cpp
@@ -61,8 +61,12 @@ void DestinationGLCanvas::doDraw(QPainter* painter)
 //    }
 //  }
 
-  glPushMatrix();
 
+  MainWindow &mainwindow = MainWindow::getInstance();
+  if ((&mainwindow) == NULL)
+    return;
+
+  glPushMatrix();
   MappingManager& mappingManager = MainWindow::getInstance().getMappingManager();
   QVector<Mapping::ptr> mappings = mappingManager.getVisibleMappings();
   for (QVector<Mapping::ptr>::const_iterator it = mappings.begin(); it != mappings.end(); ++it)
diff --git a/MainWindow.cpp b/MainWindow.cpp
index 98b6a39..7694ac9 100644
--- a/MainWindow.cpp
+++ b/MainWindow.cpp
@@ -28,6 +28,7 @@ MainWindow* MainWindow::instance = 0;
 
 MainWindow::MainWindow()
 {
+  MainWindow::setInstance(this);
   // Create model.
   mappingManager = new MappingManager;
 
@@ -60,7 +61,7 @@ MainWindow::MainWindow()
 
 MainWindow& MainWindow::getInstance()
 {
-  Q_ASSERT(instance);
+  //Q_ASSERT(instance);
 
   return *instance;
 }
diff --git a/main.cpp b/main.cpp
index 55983ad..28e7acc 100644
--- a/main.cpp
+++ b/main.cpp
@@ -23,7 +23,6 @@ int main(int argc, char *argv[])
   app.installTranslator(&translator);
 
   MainWindow win;
-  MainWindow::setInstance(&win);
 
   //win.setLocale(QLocale("fr"));