diff --git a/var/spack/packages/py-dateutil/package.py b/var/spack/packages/py-dateutil/package.py
index 11699e07ee5..3bd2f2ca139 100644
--- a/var/spack/packages/py-dateutil/package.py
+++ b/var/spack/packages/py-dateutil/package.py
@@ -9,6 +9,7 @@ class PyDateutil(Package):
 
     extends('python')
     depends_on('py-setuptools')
+    depends_on('py-six')
 
     def install(self, spec, prefix):
         python('setup.py', 'install', '--prefix=%s' % prefix)
diff --git a/var/spack/packages/py-six/package.py b/var/spack/packages/py-six/package.py
index 04d29adcedf..05c5bd00a98 100644
--- a/var/spack/packages/py-six/package.py
+++ b/var/spack/packages/py-six/package.py
@@ -8,6 +8,7 @@ class PySix(Package):
     version('1.9.0', '476881ef4012262dfc8adc645ee786c4')
 
     extends('python')
+    depends_on('py-setuptools')
 
     def install(self, spec, prefix):
         python('setup.py', 'install', '--prefix=%s' % prefix)