diff --git a/src/operator/contrib/multibox_detection.cc b/src/operator/contrib/multibox_detection.cc
index 65fe5f1208bb..37bb5a500d71 100644
--- a/src/operator/contrib/multibox_detection.cc
+++ b/src/operator/contrib/multibox_detection.cc
@@ -98,8 +98,7 @@ inline void MultiBoxDetectionForward(const Tensor<cpu, 3, DType> &out,
   const DType *p_anchor = anchors.dptr_;
 
   const int omp_threads = mxnet::engine::OpenMP::Get()->GetRecommendedOMPThreadCount();
-  std::vector<DType> outputs;
-  outputs.reserve(num_anchors * 6);
+  std::vector<DType> outputs(num_anchors * 6);
   for (int nbatch = 0; nbatch < num_batches; ++nbatch) {
     const DType *p_cls_prob = cls_prob.dptr_ + nbatch * num_classes * num_anchors;
     const DType *p_loc_pred = loc_pred.dptr_ + nbatch * num_anchors * 4;