diff --git a/.travis/test-wheels.sh b/.travis/test-wheels.sh
index 6e3fb6a0c..394b649da 100755
--- a/.travis/test-wheels.sh
+++ b/.travis/test-wheels.sh
@@ -54,6 +54,14 @@ if [[ "$platform" == "linux" ]]; then
   # Run a simple test script to make sure that the wheel works.
   $HOME/miniconda3/bin/python $TEST_SCRIPT
 
+  # Check that the other wheels are present.
+  NUMBER_OF_WHEELS=$(ls -1q $ROOT_DIR/../.whl/*.whl | wc -l)
+  if [[ "$NUMBER_OF_WHEELS" != "5" ]]; then
+    echo "Wrong number of wheels found."
+    ls -l $ROOT_DIR/../.whl/
+    exit 1
+  fi
+
 elif [[ "$platform" == "macosx" ]]; then
   MACPYTHON_PY_PREFIX=/Library/Frameworks/Python.framework/Versions
   PY_MMS=("2.7"
diff --git a/python/setup.py b/python/setup.py
index cf0f8cecd..b5cef5f78 100644
--- a/python/setup.py
+++ b/python/setup.py
@@ -81,7 +81,6 @@ setup(name="ray",
       # The BinaryDistribution argument triggers build_ext.
       distclass=BinaryDistribution,
       install_requires=["numpy",
-                        "cython",
                         "funcsigs",
                         "click",
                         "colorama",
@@ -91,6 +90,7 @@ setup(name="ray",
                         # The six module is required by pyarrow.
                         "six >= 1.0.0",
                         "flatbuffers"],
+      setup_requires=["cython >= 0.23"],
       entry_points={"console_scripts": ["ray=ray.scripts.scripts:main"]},
       include_package_data=True,
       zip_safe=False,