diff --git a/setup.py b/setup.py
index ab7aded3da460941b7c72ec3af0dd12b41e55924..0901b20b3bedc34cc964253e505fea43f17c8f64 100644
--- a/setup.py
+++ b/setup.py
@@ -17,7 +17,8 @@ else:
 if sys.version_info < (3, 0):
     reqlist = ['numpy', 'astropy >= 0.4, <3.0']
 else:
-    reqlist = ['numpy', 'astropy >= 0.4']
+    # Require astropy v3.2 or later to get much faster copies
+    reqlist = ['numpy', 'astropy >= 3.2']
 if build_c_extentions:
     reqlist.append('pybind11>=2.2.0')
     ext_modules = [Extension('lsmtool.operations._grouper',