diff --git a/gui_qt/mainwindow.cpp b/gui_qt/mainwindow.cpp
index 13e9f91..0e31607 100644
--- a/gui_qt/mainwindow.cpp
+++ b/gui_qt/mainwindow.cpp
@@ -87,6 +87,6 @@ void MainWindow::quickPreview()
 {
     DialogRender* dialog = new DialogRender(this);
     dialog->startRender(3, 400, 300);
-    
+
     delete dialog;
 }
diff --git a/gui_qt/preview.cpp b/gui_qt/preview.cpp
index 2a86015..571ac56 100644
--- a/gui_qt/preview.cpp
+++ b/gui_qt/preview.cpp
@@ -70,6 +70,11 @@ Preview::~Preview()
     delete pixbuf;
 }
 
+QColor Preview::getColor(double x, double y)
+{
+    return QColor(0, 0, 0);
+}
+
 void Preview::doRender()
 {
     if (this->alive)
diff --git a/gui_qt/preview.h b/gui_qt/preview.h
index 554c169..052ec95 100644
--- a/gui_qt/preview.h
+++ b/gui_qt/preview.h
@@ -21,7 +21,7 @@ public:
 protected:
     void resizeEvent(QResizeEvent* event);
     void paintEvent(QPaintEvent* event);
-    virtual QColor getColor(double x, double y) = 0;
+    virtual QColor getColor(double x, double y);
 
     void renderPixbuf();
     void forceRender();