diff --git a/setup.py b/setup.py
index f85d7b8..79891cd 100644
--- a/setup.py
+++ b/setup.py
@@ -23,7 +23,8 @@
     author = "Ian Heywood & RATT",
     author_email = "ian.heywood@physics.ox.ac.uk",
     url = "https://github.com/ratt-ru/shadeMS",
-    packages=find_packages(), 
+    packages=find_packages(),
+    python_requires='>=3.5',
     install_requires = requirements,
     include_package_data = True,
     scripts=["bin/" + i for i in os.listdir("bin")],