diff --git a/BERT/Custom_Named_Entity_Recognition_with_BERT.ipynb b/BERT/Custom_Named_Entity_Recognition_with_BERT.ipynb
index 956d6b6f..6b81a6b2 100644
--- a/BERT/Custom_Named_Entity_Recognition_with_BERT.ipynb
+++ b/BERT/Custom_Named_Entity_Recognition_with_BERT.ipynb
@@ -4131,7 +4131,7 @@
         "        # step 2: add special tokens (and corresponding labels)\n",
         "        tokenized_sentence = [\"[CLS]\"] + tokenized_sentence + [\"[SEP]\"] # add special tokens\n",
         "        labels.insert(0, \"O\") # add outside label for [CLS] token\n",
-        "        labels.insert(-1, \"O\") # add outside label for [SEP] token\n",
+        "        labels.append(\"O\") # add outside label for [SEP] token\n",
         "\n",
         "        # step 3: truncating/padding\n",
         "        maxlen = self.max_len\n",
@@ -5710,4 +5710,4 @@
       ]
     }
   ]
-}
\ No newline at end of file
+}