diff --git a/var/spack/repos/builtin/packages/py-backports-shutil-get-terminal-size/package.py b/var/spack/repos/builtin/packages/py-backports-shutil-get-terminal-size/package.py
index 5950faa765..3447666a2e 100644
--- a/var/spack/repos/builtin/packages/py-backports-shutil-get-terminal-size/package.py
+++ b/var/spack/repos/builtin/packages/py-backports-shutil-get-terminal-size/package.py
@@ -34,5 +34,7 @@ class PyBackportsShutilGetTerminalSize(PythonPackage):
 
     version('1.0.0', '03267762480bd86b50580dc19dff3c66')
 
-    depends_on('py-setuptools', type='build')
+    # newer setuptools version mess with "namespace" packages in an
+    # incompatible way cf. https://github.com/pypa/setuptools/issues/900
+    depends_on('py-setuptools@:30.999.999', type='build')
     depends_on('python@:3.2.999')
diff --git a/var/spack/repos/builtin/packages/py-backports-ssl-match-hostname/package.py b/var/spack/repos/builtin/packages/py-backports-ssl-match-hostname/package.py
index bf4679556b..12af938be6 100644
--- a/var/spack/repos/builtin/packages/py-backports-ssl-match-hostname/package.py
+++ b/var/spack/repos/builtin/packages/py-backports-ssl-match-hostname/package.py
@@ -33,4 +33,6 @@ class PyBackportsSslMatchHostname(PythonPackage):
 
     version('3.5.0.1', 'c03fc5e2c7b3da46b81acf5cbacfe1e6')
 
-    depends_on('py-setuptools', type='build')
+    # newer setuptools version mess with "namespace" packages in an
+    # incompatible way cf. https://github.com/pypa/setuptools/issues/900
+    depends_on('py-setuptools@:30.999.999', type='build')