diff --git a/setup.py b/setup.py
index 0901b20b3bedc34cc964253e505fea43f17c8f64..81b22d3d4372da0b6ae8f5a842557030055d3765 100644
--- a/setup.py
+++ b/setup.py
@@ -17,8 +17,9 @@ else:
 if sys.version_info < (3, 0):
     reqlist = ['numpy', 'astropy >= 0.4, <3.0']
 else:
-    # Require astropy v3.2 or later to get much faster copies
-    reqlist = ['numpy', 'astropy >= 3.2']
+    # Require astropy v3.2 or later to get much faster copies (4.x can cause some
+    # installation problems, so exclude for now)
+    reqlist = ['numpy', 'astropy >= 3.2, <4.0']
 if build_c_extentions:
     reqlist.append('pybind11>=2.2.0')
     ext_modules = [Extension('lsmtool.operations._grouper',