diff --git "a/264_BERT\351\242\204\350\256\255\347\273\203.ipynb" "b/264_BERT\351\242\204\350\256\255\347\273\203.ipynb"
index a58e50e..36b1691 100644
--- "a/264_BERT\351\242\204\350\256\255\347\273\203.ipynb"
+++ "b/264_BERT\351\242\204\350\256\255\347\273\203.ipynb"
@@ -565,7 +565,7 @@
     "            if random.random() < 0.5:\n",
     "                masked_token = tokens[mlm_pred_position]\n",
     "            else:\n",
-    "                masked_token = random.randint(0, len(vocab) - 1)\n",
+    "                masked_token = random.choice(vocab.idx_to_token)\n",
     "        mlm_input_tokens[mlm_pred_position] = masked_token\n",
     "        pred_positions_and_labels.append((mlm_pred_position, tokens[mlm_pred_position]))  \n",
     "    return mlm_input_tokens, pred_positions_and_labels\n",