diff --git a/paddlehub/module/nlp_module.py b/paddlehub/module/nlp_module.py
index 65479b14d207ad6332d37511938176c8314ff047..f99a672d204dca47285c7ff452c83bc9ca64a8a8 100644
--- a/paddlehub/module/nlp_module.py
+++ b/paddlehub/module/nlp_module.py
@@ -111,7 +111,7 @@ class NLPPredictionModule(NLPBaseModule):
         if six.PY2:
             unicode_texts = []
             for text in texts:
-                if not isinstance(text, six.string_types):
+                if isinstance(text, six.string_types):
                     unicode_texts.append(
                         text.decode(sys_stdin_encoding()).decode("utf8"))
                 else:
diff --git a/paddlehub/serving/app_single.py b/paddlehub/serving/app_single.py
index f9e308ef16b2f5f0b5024a449691ec964b78e4d8..a6975295c53e51b3535bd8255184bf0847635bb9 100644
--- a/paddlehub/serving/app_single.py
+++ b/paddlehub/serving/app_single.py
@@ -427,7 +427,7 @@ def create_app(init_flag=False, configs=None):
             return {"error": "Module {} is not available.".format(module_name)}
         module_info = nlp_module_info.get_module_info(module_name)
         if module_info["code_version"] == "v2":
-            results = "This usage is out of date, please use 'application/json' as content-type to post to /predict/%s. See 'https://github.com/PaddlePaddle/PaddleHub/blob/release/v1.5/docs/tutorial/serving.md' for more details." % (
+            results = "This usage is out of date, please use 'application/json' as content-type to post to /predict/%s. See 'https://github.com/PaddlePaddle/PaddleHub/blob/release/v1.6/docs/tutorial/serving.md' for more details." % (
                 module_name)
             return gen_result("-1", results, "")
         req_id = request.data.get("id")
@@ -460,7 +460,7 @@ def create_app(init_flag=False, configs=None):
             return gen_result("-1", msg, "")
         inputs = request.json
         if inputs is None:
-            results = "This usage is out of date, please use 'application/json' as content-type to post to /predict/%s. See 'https://github.com/PaddlePaddle/PaddleHub/blob/release/v1.5/docs/tutorial/serving.md' for more details." % (
+            results = "This usage is out of date, please use 'application/json' as content-type to post to /predict/%s. See 'https://github.com/PaddlePaddle/PaddleHub/blob/release/v1.6/docs/tutorial/serving.md' for more details." % (
                 module_name)
             return gen_result("-1", results, "")