diff --git a/src/ViewportWidget.h b/src/ViewportWidget.h
index 3bbdefb..e67c0c8 100644
--- a/src/ViewportWidget.h
+++ b/src/ViewportWidget.h
@@ -82,6 +82,7 @@ protected:
     void resizeGL(int w, int h) override;
 
     void mousePressEvent(QMouseEvent *event) override;
+    void mouseReleaseEvent(QMouseEvent *event) override;
     void mouseMoveEvent(QMouseEvent *event) override;
     void wheelEvent(QWheelEvent *event) override;
     void keyPressEvent(QKeyEvent *event) override;