diff --git a/paddle/gserver/layers/DetectionOutputLayer.cpp b/paddle/gserver/layers/DetectionOutputLayer.cpp
index 0cf0a92bf4..570117de65 100644
--- a/paddle/gserver/layers/DetectionOutputLayer.cpp
+++ b/paddle/gserver/layers/DetectionOutputLayer.cpp
@@ -143,7 +143,8 @@ void DetectionOutputLayer::forward(PassType passType) {
     resetOutput(numKept, 7);
   } else {
     MatrixPtr outV = getOutputValue();
-    outV = NULL;
+    if (outV)
+      outV->resize(0,0);
     return;
   }
   MatrixPtr outV = getOutputValue();
diff --git a/python/paddle/trainer_config_helpers/layers.py b/python/paddle/trainer_config_helpers/layers.py
index 8c7d1738ad..9bdcca1716 100644
--- a/python/paddle/trainer_config_helpers/layers.py
+++ b/python/paddle/trainer_config_helpers/layers.py
@@ -1224,8 +1224,8 @@ def detection_output_layer(input_loc,
                            name=None):
     """
     Apply the NMS to the output of network and compute the predict bounding
-    box location. The output of this layer could be None if there is no valid
-    bounding box.
+    box location. The output's shape of this layer could be zero if there is
+    no valid bounding box.
 
     :param name: The Layer Name.
     :type name: basestring