diff --git a/src/api/operator/numpy/np_matrix_op.cc b/src/api/operator/numpy/np_matrix_op.cc
index e2fb1230c2d9..9075e153161c 100644
--- a/src/api/operator/numpy/np_matrix_op.cc
+++ b/src/api/operator/numpy/np_matrix_op.cc
@@ -527,7 +527,7 @@ MXNET_REGISTER_API("_npi.vstack")
     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);
+  auto ndoutputs = Invoke(op, &attrs, param.num_args, inputs, &num_outputs, nullptr);
   *ret = ndoutputs[0];
 });
 
diff --git a/src/api/operator/numpy/random/np_multinomial_op.cc b/src/api/operator/numpy/random/np_multinomial_op.cc
index cbd7c5977fd4..5f4a3f2a1a44 100644
--- a/src/api/operator/numpy/random/np_multinomial_op.cc
+++ b/src/api/operator/numpy/random/np_multinomial_op.cc
@@ -35,14 +35,19 @@ MXNET_REGISTER_API("_npi.multinomial")
   const nnvm::Op* op = Op::Get("_npi_multinomial");
   nnvm::NodeAttrs attrs;
   op::NumpyMultinomialParam param;
-  std::vector<NDArray*> inputs;
+  NDArray** inputs = new NDArray*[1]();
+  int num_inputs = 0;
 
-  //parse int
+  // parse int
   param.n = arg[0].operator int();
 
   // parse pvals
   if (args[1].type_code() == kNull) {
     param.pvals = dmlc::nullopt;
+  } else if (args[1].type_code() == kNDArrayHandle) {
+    param.pvals = dmlc::nullopt;
+    inputs[0] = args[1].operator mxnet::NDArray*();
+    num_inputs = 1;
   } else {
     param.pvals = Tuple<double>(args[1].operator ObjectRef());
   }
@@ -61,7 +66,8 @@ MXNET_REGISTER_API("_npi.multinomial")
   attrs.parsed = std::move(param);
   attrs.op = op;
   SetAttrDict<op::NumpyMultinomialParam>(&attrs);
-  auto ndoutputs = Invoke(op, &attrs, 0, nullptr, 0, nullptr);
+  inputs = num_inputs == 0 ? nullptr : inputs;
+  auto ndoutputs = Invoke(op, &attrs, num_inputs, inputs, 0, nullptr);
   *ret = ndoutputs[0];
 
 });