diff --git a/include/xgboost/base.h b/include/xgboost/base.h
index 24ff4d397..3d346b43e 100644
--- a/include/xgboost/base.h
+++ b/include/xgboost/base.h
@@ -9,6 +9,7 @@
 #include <dmlc/base.h>
 #include <dmlc/omp.h>
 #include <cmath>
+#include <iostream>
 
 /*!
  * \brief string flag for R library, to leave hooks when needed.
diff --git a/tests/cpp/predictor/test_gpu_predictor.cu b/tests/cpp/predictor/test_gpu_predictor.cu
index 3aa5f6f8a..1a4a48f83 100644
--- a/tests/cpp/predictor/test_gpu_predictor.cu
+++ b/tests/cpp/predictor/test_gpu_predictor.cu
@@ -15,6 +15,9 @@ TEST(gpu_predictor, Test) {
   std::unique_ptr<Predictor> cpu_predictor =
       std::unique_ptr<Predictor>(Predictor::Create("cpu_predictor"));
 
+  gpu_predictor->Init({}, {});
+  cpu_predictor->Init({}, {});
+
   std::vector<std::unique_ptr<RegTree>> trees;
   trees.push_back(std::unique_ptr<RegTree>(new RegTree()));
   trees.back()->InitModel();
diff --git a/tests/cpp/tree/test_gpu_hist.cu b/tests/cpp/tree/test_gpu_hist.cu
index a6e34b0ce..c07e33732 100644
--- a/tests/cpp/tree/test_gpu_hist.cu
+++ b/tests/cpp/tree/test_gpu_hist.cu
@@ -22,9 +22,10 @@ TEST(gpu_hist_experimental, TestSparseShard) {
   hmat.Init(dmat.get(), max_bins);
   gmat.cut = &hmat;
   gmat.Init(dmat.get());
-  ncclComm_t comm;
+  TrainParam p;
+  p.max_depth = 6;
   DeviceShard shard(0, 0, gmat, 0, rows, hmat.row_ptr.back(),
-                    TrainParam());
+                    p);
 
   ASSERT_LT(shard.row_stride, columns);
 
@@ -56,9 +57,10 @@ TEST(gpu_hist_experimental, TestDenseShard) {
   hmat.Init(dmat.get(), max_bins);
   gmat.cut = &hmat;
   gmat.Init(dmat.get());
-  ncclComm_t comm;
+  TrainParam p;
+  p.max_depth = 6;
   DeviceShard shard(0, 0, gmat, 0, rows, hmat.row_ptr.back(),
-                    TrainParam());
+                    p);
 
   ASSERT_EQ(shard.row_stride, columns);