diff --git a/module3/exo1/analyse-syndrome-grippal.ipynb b/module3/exo1/analyse-syndrome-grippal.ipynb
index 6f5ec0a5d9e437196a6f35104c7eec11e0e8b982..50cb61283eed2953f95146e2d61fdaaafdff73f4 100644
--- a/module3/exo1/analyse-syndrome-grippal.ipynb
+++ b/module3/exo1/analyse-syndrome-grippal.ipynb
@@ -47,7 +47,8 @@
     "\n",
     "import os\n",
     "import urllib.request\n",
-    "urllib.request.urlretrieve(data_url, data_file)"
+    "if not os.path.exists(data_file):\n",
+    "    urllib.request.urlretrieve(data_url, data_file)"
    ]
   },
   {