diff --git a/setup.py b/setup.py
index 211275a..7c483a6 100644
--- a/setup.py
+++ b/setup.py
@@ -11,7 +11,7 @@
     license='ISC',
     packages=find_packages(),
     keywords='human numbers format notation scientific engineering',
-    install_requires=[],
+    install_requires=['future'],
     test_suite='ballpark.tests',
     classifiers=[
         'Development Status :: 4 - Beta',