diff --git a/setup.py b/setup.py
index 5f44f2f..c43766a 100644
--- a/setup.py
+++ b/setup.py
@@ -25,12 +25,12 @@ if mo:
 else:
     raise RuntimeError("Unable to find version string in %s." % (VERSIONFILE,))
 
-# Use README.md as the package long description  
+# Use README.md as the package long description
 with open('README.md') as f:
     long_description = f.read()
 
 class CustomBuildExtCommand(build_ext):
-    """ This extension command lets us not require numpy be installed before running pip install ripser 
+    """ This extension command lets us not require numpy be installed before running pip install ripser
         build_ext command for use when numpy headers are needed.
     """
 
@@ -52,11 +52,11 @@ if platform.system() == "Windows":
     ])
 elif platform.system() == "Darwin":
     extra_compile_args.extend([
-        '-std=c++11', 
+        '-std=c++11',
         "-mmacosx-version-min=10.9"
     ])
     extra_link_args.extend([
-        "-stdlib=libc++", 
+        "-stdlib=libc++",
         "-mmacosx-version-min=10.9"
     ])
 else:
@@ -104,7 +104,7 @@ setup(
     url="https://ripser.scikit-tda.org",
     license='MIT',
     packages=['ripser'],
-    ext_modules=cythonize(ext_modules),
+    ext_modules=cythonize(ext_modules, language_level = '3'),
     install_requires=[
         'Cython',
         'numpy',
@@ -114,7 +114,7 @@ setup(
     ],
     extras_require={
         'testing': [ # `pip install -e ".[testing]"``
-            'pytest'  
+            'pytest'
         ],
         'docs': [ # `pip install -e ".[docs]"`
             'sktda_docs_config'