diff --git a/python/paddle/v2/layer.py b/python/paddle/v2/layer.py
index f6b3dbf39a515d8780835c08ae77224f15717ac1..67b7192bb74b7440567a27df1394a754027f702f 100644
--- a/python/paddle/v2/layer.py
+++ b/python/paddle/v2/layer.py
@@ -235,9 +235,9 @@ def __trim_submodel__(old_submodel, layer_names, input_layer_names,
 def parse_network(output_layers, extra_layers=None):
     if not isinstance(output_layers, collections.Sequence):
         output_layers = [output_layers]
-    if extra_layers is not None and not isinstance(extra_layers,
-                                                   collections.Sequence):
-        extra_layers = [extra_layers]
+    if extra_layers is not None:
+        if not isinstance(extra_layers, collections.Sequence):
+            extra_layers = [extra_layers]
     else:
         extra_layers = []
 
diff --git a/python/paddle/v2/topology.py b/python/paddle/v2/topology.py
index 67e5535a0cc73b33297b01c6083623345108934f..5109dc58fe5128ab4144224f76190c5cfdb69f6a 100644
--- a/python/paddle/v2/topology.py
+++ b/python/paddle/v2/topology.py
@@ -31,7 +31,6 @@ class Topology(object):
     def __init__(self, layers, extra_layers=None):
         def __check__(layers):
             if not isinstance(layers, collections.Sequence):
-                __check_layer_type__(layers)
                 layers = [layers]
             for layer in layers:
                 __check_layer_type__(layer)