diff --git a/damo/utils/visualize.py b/damo/utils/visualize.py
index cfba883..40a493c 100644
--- a/damo/utils/visualize.py
+++ b/damo/utils/visualize.py
@@ -27,6 +27,8 @@ def vis(img, boxes, scores, cls_ids, conf=0.5, class_names=None):
         font = cv2.FONT_HERSHEY_SIMPLEX
 
         txt_size = cv2.getTextSize(text, font, 0.4, 1)[0]
+        
+        img = img.copy()  # Ensure img is writable
         cv2.rectangle(img, (x0, y0), (x1, y1), color, 2)
 
         txt_bk_color = (_COLORS[cls_id] * 255 * 0.7).astype(np.uint8).tolist()