diff --git a/python/paddle/v2/fluid/layers/nn.py b/python/paddle/v2/fluid/layers/nn.py
index 0b64e09cd359fc89ddc868ae87c1afdbfface541..5ebd329fc0285a39111a23b3c58c80944cfe23f6 100644
--- a/python/paddle/v2/fluid/layers/nn.py
+++ b/python/paddle/v2/fluid/layers/nn.py
@@ -185,7 +185,7 @@ def fc(input,
         helper.append_op(
             type="sum", inputs={"X": mul_results}, outputs={"Out": pre_bias})
     # add bias
-    pre_activation = helper.append_bias_op(pre_bias)
+    pre_activation = helper.append_bias_op(pre_bias, dim_start=num_flatten_dims)
     # add activation
     return helper.append_activation(pre_activation)