diff --git a/python/paddle/nn/functional/loss.py b/python/paddle/nn/functional/loss.py
index 831d5e9207d0d8ab7796b4cfdba982fab3fd3359..3f12fb759d16a236d3292f6c0fb580300ffce211 100755
--- a/python/paddle/nn/functional/loss.py
+++ b/python/paddle/nn/functional/loss.py
@@ -1653,12 +1653,16 @@ def cross_entropy(input,
         if soft_label == False:
             valid_label = paddle.where(label == ignore_index,
                                        paddle.zeros_like(label), label)
+            # TODO: Temporarily use paddle.nonzero instead of paddle.max 
+            # to detect and find out possible illegal label values
             if len(paddle.nonzero(valid_label < 0)) > 0:
                 invalid_label = paddle.gather_nd(
                     valid_label, paddle.nonzero(valid_label < 0))
                 raise ValueError(
                     "Target({}) is out of class_dimension's lower bound({})".
                     format(invalid_label[0], 0))
+            # TODO: Temporarily use paddle.nonzero instead of paddle.max 
+            # to detect and find out possible illegal label values
             if len(paddle.nonzero(valid_label >= input.shape[-1])) > 0:
                 invalid_label = paddle.gather_nd(
                     valid_label, paddle.nonzero(valid_label >= input.shape[-1]))