diff --git a/pupil_src/capture/pupil_detectors/visualizer_3d.py b/pupil_src/capture/pupil_detectors/visualizer_3d.py
index 360bdbe930..ac1b659094 100644
--- a/pupil_src/capture/pupil_detectors/visualizer_3d.py
+++ b/pupil_src/capture/pupil_detectors/visualizer_3d.py
@@ -370,6 +370,8 @@ def update_window(self, g_pool, result  ):
 
 		if self._window != None:
 			glfwMakeContextCurrent(self._window)
+		else:
+			return
 
 		self.image_width , self.image_height = g_pool.capture.frame_size