diff --git a/setup.py b/setup.py
index 7e50c71..9874871 100644
--- a/setup.py
+++ b/setup.py
@@ -22,7 +22,7 @@
     version=version,
     author='Elizabeth Tseng',
     author_email='etseng@pacb.com',
-    ext_modules = cythonize(ext_modules),
+    ext_modules = cythonize(ext_modules, language_level = "2"),
     include_dirs = [np.get_include()],
     zip_safe=False,
     packages = ['cupcake', 'cupcake.io', 'cupcake.ice',