diff --git a/.travis.yml b/.travis.yml
index 5f6f052..7ebbb8e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -15,15 +15,21 @@ matrix:
   - python: 2.7
   - os: osx
     language: generic
+    before_install:
+      - brew update
+      - brew upgrade python
+      - brew install python2
+      - pip install virtualenv
+      - python2 -m virtualenv env
+      - source env/bin/activate
   - os: osx
     language: generic
     before_install:
-    - brew update
-    - brew install python3
-    - virtualenv env -p python3
-    - source env/bin/activate
-  - sudo: required
-    services:
+      - brew update
+      - brew upgrade python
+      - python3 -m venv env
+      - source env/bin/activate
+  - services:
     - docker
     env: DOCKER_IMAGE=quay.io/pypa/manylinux1_x86_64
     install:
@@ -34,8 +40,7 @@ matrix:
     - if [[ $TRAVIS_TAG ]]; then pip install twine && twine upload -u datamade.wheelbuilder
       -p $PYPIPASSWORD --skip-existing wheelhouse/*; fi
     - exit 0
-  - sudo: required
-    services:
+  - services:
     - docker
     env: DOCKER_IMAGE=quay.io/pypa/manylinux1_i686
     install:
@@ -48,9 +53,7 @@ matrix:
     - exit 0
 install:
 - pip install --upgrade pip
-- pip install numpy
-- pip freeze
-- pip install --upgrade -r requirements.txt
+- pip install -r requirements.txt
 - cython lbfgs/_lowlevel.pyx
 - pip install -e .
 script:
diff --git a/setup.py b/setup.py
index bf71909..eae0220 100644
--- a/setup.py
+++ b/setup.py
@@ -3,6 +3,15 @@
 from setuptools import setup, Extension
 from setuptools.command.build_ext import build_ext
 from distutils.ccompiler import get_default_compiler
+import numpy
+
+try:
+    from Cython.Build import cythonize
+
+    use_cython = True
+except ImportError:
+    use_cython = False
+
 
 class custom_build_ext(build_ext):
     def finalize_options(self):
@@ -16,34 +25,17 @@ def finalize_options(self):
             include_dirs.append('compat/win32')
 
 
+include_dirs = ['liblbfgs'] + [numpy.get_include()]
 
-# from Michael Hoffman's http://www.ebi.ac.uk/~hoffman/software/sunflower/
-class NumpyExtension(Extension):
-
-    def __init__(self, *args, **kwargs):
-        Extension.__init__(self, *args, **kwargs)
-
-        self._include_dirs = self.include_dirs
-        del self.include_dirs  # restore overwritten property
-
-    # warning: Extension is a classic class so it's not really read-only
-
-    def get_include_dirs(self):
-        from numpy import get_include
-
-        return self._include_dirs + [get_include()]
-
-    def set_include_dirs(self, value):
-        self._include_dirs = value
-
-    def del_include_dirs(self):
-        pass
-        
-    include_dirs = property(get_include_dirs, 
-                            set_include_dirs, 
-                            del_include_dirs)
-
-include_dirs = ['liblbfgs']
+if use_cython:
+    ext_modules = cythonize(
+        [Extension('lbfgs._lowlevel',
+                    ['lbfgs/_lowlevel.pyx', 'liblbfgs/lbfgs.c'],
+                    include_dirs=include_dirs)])
+else:
+    ext_modules = [Extension('lbfgs._lowlevel',
+                              ['lbfgs/_lowlevel.c', 'liblbfgs/lbfgs.c'],
+                              include_dirs=include_dirs)]
 
 setup(
     name="PyLBFGS",
@@ -53,9 +45,7 @@ def del_include_dirs(self):
     author_email="fgregg@gmail.com",
     packages=['lbfgs'],
     install_requires=['numpy>=1.12.1'],
-    ext_modules=[NumpyExtension('lbfgs._lowlevel', 
-                                ['lbfgs/_lowlevel.c', 'liblbfgs/lbfgs.c'],
-                                include_dirs=include_dirs)],
+    ext_modules=ext_modules,
     classifiers=[
         "Intended Audience :: Developers",
         "Intended Audience :: Science/Research",
@@ -68,4 +58,3 @@ def del_include_dirs(self):
     ],
     cmdclass={'build_ext': custom_build_ext},
 )
-