diff --git a/pytorch_pretrained_bert/modeling.py b/pytorch_pretrained_bert/modeling.py
index d7cc37e1..b9b68371 100644
--- a/pytorch_pretrained_bert/modeling.py
+++ b/pytorch_pretrained_bert/modeling.py
@@ -1052,8 +1052,8 @@ class BertForMultipleChoice(BertPreTrainedModel):
 
     def forward(self, input_ids, token_type_ids=None, attention_mask=None, labels=None):
         flat_input_ids = input_ids.view(-1, input_ids.size(-1))
-        flat_token_type_ids = token_type_ids.view(-1, token_type_ids.size(-1))
-        flat_attention_mask = attention_mask.view(-1, attention_mask.size(-1))
+        flat_token_type_ids = token_type_ids.view(-1, token_type_ids.size(-1)) if token_type_ids is not None else None
+        flat_attention_mask = attention_mask.view(-1, attention_mask.size(-1)) if attention_mask is not None else None
         _, pooled_output = self.bert(flat_input_ids, flat_token_type_ids, flat_attention_mask, output_all_encoded_layers=False)
         pooled_output = self.dropout(pooled_output)
         logits = self.classifier(pooled_output)