diff --git a/src/api/operator/numpy/np_elemwise_broadcast_logic_op.cc b/src/api/operator/numpy/np_elemwise_broadcast_logic_op.cc
index 87b57af72e46..bf68418bd7af 100644
--- a/src/api/operator/numpy/np_elemwise_broadcast_logic_op.cc
+++ b/src/api/operator/numpy/np_elemwise_broadcast_logic_op.cc
@@ -76,7 +76,8 @@ MXNET_REGISTER_API("_npi.greater")
   using namespace runtime;
   const nnvm::Op* op = Op::Get("_npi_greater");
   const nnvm::Op* op_scalar = Op::Get("_npi_greater_scalar");
-  UFuncHelper(args, ret, op, op_scalar, nullptr);
+  const nnvm::Op* op_rscalar = Op::Get("_npi_greater_scalar");
+  UFuncHelper(args, ret, op, op_scalar, op_rscalar);
 });
 
 }  // namespace mxnet
diff --git a/src/api/operator/numpy/np_matrix_op.cc b/src/api/operator/numpy/np_matrix_op.cc
index d95879db6fa5..e2fb1230c2d9 100644
--- a/src/api/operator/numpy/np_matrix_op.cc
+++ b/src/api/operator/numpy/np_matrix_op.cc
@@ -522,10 +522,11 @@ MXNET_REGISTER_API("_npi.vstack")
   attrs.op = op;
   SetAttrDict<op::NumpyVstackParam>(&attrs);
   int num_outputs = 0;
-  std::vector<NDArray*> inputs;
-  for (int i = 0; i < param.num_args; ++i) {
-    inputs.push_back(args[i].operator mxnet::NDArray*());
+  std::vector<NDArray*> inputs_vec(args.size(), nullptr);
+  for (int i = 0; i < args_size; ++i) {
+    inputs_vec[i] = args[i].operator mxnet::NDArray*();
   }
+  NDArray** inputs = inputs_vec.data();
   auto ndoutputs = Invoke(op, &attrs, param.num_args, &inputs[0], &num_outputs, nullptr);
   *ret = ndoutputs[0];
 });