diff --git a/python/paddle/trainer_config_helpers/evaluators.py b/python/paddle/trainer_config_helpers/evaluators.py
index 179a3a053a961126adcb750519c399f28a441867..985fae9f955c950d861d4f1f2f98845562fb6fc9 100644
--- a/python/paddle/trainer_config_helpers/evaluators.py
+++ b/python/paddle/trainer_config_helpers/evaluators.py
@@ -310,9 +310,10 @@ def ctc_error_evaluator(
 
     :param name: Evaluator name.
     :type name: None|basestring
-    :param input: Input Layer.
+    :param input: Input Layer. Should be the same as the input for ctc_layer.
     :type input: LayerOutput
-    :param label: input label, which is a data_layer.
+    :param label: input label, which is a data_layer. Should be the same as the
+                  label for ctc_layer
     :type label: LayerOutput
     """
     evaluator_base(name=name,
diff --git a/python/paddle/trainer_config_helpers/tests/layers_test_config.py b/python/paddle/trainer_config_helpers/tests/layers_test_config.py
index d479fb263fb66e67a56d23d9d4c1e21ca9052699..763993231f72f5e53e0d89044e68e8774db5ba36 100644
--- a/python/paddle/trainer_config_helpers/tests/layers_test_config.py
+++ b/python/paddle/trainer_config_helpers/tests/layers_test_config.py
@@ -41,7 +41,7 @@ tmp = fc_layer(input=x1,
 ctc = ctc_layer(input=tmp,
                 label=y,
                 size=num_classes + 1)
-ctc_eval = ctc_error_evaluator(input=ctc, label=y)
+ctc_eval = ctc_error_evaluator(input=tmp, label=y)
 
 settings(
     batch_size=10,