diff --git a/paddle/gserver/layers/SequenceConcatLayer.cpp b/paddle/gserver/layers/SequenceConcatLayer.cpp
index b4677687a6cc7755fdb7584a9524de9b65a0c627..599706eb419ede72dbd6f4c8c74e57f5f9965388 100644
--- a/paddle/gserver/layers/SequenceConcatLayer.cpp
+++ b/paddle/gserver/layers/SequenceConcatLayer.cpp
@@ -168,13 +168,17 @@ void SequenceConcatLayer::backward(const UpdateCallback& callback) {
     size_t rightNumIns = 0;
     for (size_t seqId = 0; seqId < numSequences1; ++seqId) {
       leftNumIns = starts1[seqId + 1] - starts1[seqId];
-      inputGrad1->subMatrix(starts1[seqId], leftNumIns)
-          ->add(*(outputGrad->subMatrix(offset, leftNumIns)));
+      if (inputGrad1) {
+        inputGrad1->subMatrix(starts1[seqId], leftNumIns)
+            ->add(*(outputGrad->subMatrix(offset, leftNumIns)));
+      }
       offset += leftNumIns;
 
       rightNumIns = starts2[seqId + 1] - starts2[seqId];
-      inputGrad2->subMatrix(starts2[seqId], rightNumIns)
-          ->add(*(outputGrad->subMatrix(offset, rightNumIns)));
+      if (inputGrad2) {
+        inputGrad2->subMatrix(starts2[seqId], rightNumIns)
+            ->add(*(outputGrad->subMatrix(offset, rightNumIns)));
+      }
       offset += rightNumIns;
     }
   }