diff --git a/gridworld/visualizer.py b/gridworld/visualizer.py
index 77d39d5..1d0249a 100644
--- a/gridworld/visualizer.py
+++ b/gridworld/visualizer.py
@@ -80,8 +80,8 @@ def render_video(self, output,
             self.set_agent_state(*init_conds)
         fourcc = cv2.VideoWriter_fourcc(*'mp4v')
         output.parent.mkdir(exist_ok=True)
-        writer = cv2.VideoWriter(f'{output}.mp4', fourcc, fps, self.render_size)
         image = self.render()
+        writer = cv2.VideoWriter(f'{output}.mp4', fourcc, fps, image.shape[:2])
         writer.write(image[..., ::-1])
         tq = tqdm(total=len(event_sequence), disable=not verbose)
         for _, event in enumerate(event_sequence):
@@ -106,4 +106,4 @@ def postproc_video(self, output):
             os.system(f"mv {output}2.mp4 {output}.mp4")
         else:
             raise ValueError('Install the latest version of ffmpeg')
-    
\ No newline at end of file
+