diff --git a/src/main_window.cc b/src/main_window.cc
index 1c37f72..285294f 100644
--- a/src/main_window.cc
+++ b/src/main_window.cc
@@ -84,7 +84,7 @@ void MainWindow::open(const QString &path) {
 			slider, &QSlider::setValue);
 	connect(dc, &DroneController::collision, settings_pane, &SettingsPane::addCollision);
 	connect(settings_pane, &SettingsPane::sphereRadiusChanged,
-			[&](double _) { settings_pane->clearCollisions(); });
+			[&](double _) { Q_UNUSED(_); settings_pane->clearCollisions(); });
 	connect(settings_pane, &SettingsPane::sphereRadiusChanged,
 			dc, &DroneController::computeCollisions);
 	connect(settings_pane, &SettingsPane::sphereRadiusChanged,