diff --git a/run_combination_test.py b/run_combination_test.py
index 08fd4b64..5dccebb1 100755
--- a/run_combination_test.py
+++ b/run_combination_test.py
@@ -13,7 +13,7 @@
     'cuda_cudnn_nccl': docker.get_cuda_cudnn_nccl_choices('chainer'),
     'numpy': docker.get_numpy_choices(),
     'scipy': [None, '0.18', '0.19', '1.0'],
-    'protobuf': ['2', '3', 'cpp-3'],
+    'protobuf': ['3', 'cpp-3'],
     'h5py': [None, '2.5', '2.6', '2.7'],
     'pillow': [None, '3.4', '4.0', '4.1'],
     'theano': [None, '0.8', '0.9', '1.0'],