diff --git a/paddle/scripts/docker/build.sh b/paddle/scripts/docker/build.sh
index f50b793bf5e7bbb9e239287aee3277f2de8fb96b..147c0f3e647084e8f57ee2d00267fe8e626243bb 100644
--- a/paddle/scripts/docker/build.sh
+++ b/paddle/scripts/docker/build.sh
@@ -37,8 +37,13 @@ Configuring cmake in /paddle/build ...
       -DWITH_STYLE_CHECK=${WITH_STYLE_CHECK:-OFF}
       -DWITH_TESTING=${WITH_TESTING:-OFF}
       -DCMAKE_EXPORT_COMPILE_COMMANDS=ON
+      -DUNITTEST_USE_VIRTUALENV=OFF
 ========================================
 EOF
+
+# Disable UNITTEST_USE_VIRTUALENV in docker because
+# docker environment is fully controlled by this script.
+# See /Paddle/CMakeLists.txt, UNITTEST_USE_VIRTUALENV option.
 cmake .. \
       -DCMAKE_BUILD_TYPE=Release \
       -DWITH_DOC=OFF \
diff --git a/paddle/setup.py.in b/paddle/setup.py.in
index 31c9329f6a65f22b01d9a42a5cea2ce69641c583..af107e76723135124e56db52a76e4f8aff5c4acf 100644
--- a/paddle/setup.py.in
+++ b/paddle/setup.py.in
@@ -22,6 +22,8 @@ setup(name="py_paddle",
       package_data={'py_paddle':['*.py','_swig_paddle.so']},
       install_requires = [
         'nltk>=3.2.2',
+        # We use `numpy.flip` in `test_image.py`.
+        # `numpy.flip` is introduced in `1.12.0`
         'numpy>=1.12.0',      # The numpy is required.
         'protobuf==${PROTOBUF_VERSION}'    # The paddle protobuf version
       ],