diff --git a/var/spack/packages/py-dateutil/package.py b/var/spack/packages/py-dateutil/package.py
index 11699e07ee5ac0d08a0e8e5d66c45ed8acca1a29..3bd2f2ca139f2c7bf823761c377597bf7a469442 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 04d29adcedfbc3ca1478db02e950e069e1337a2c..05c5bd00a9831a5c9dc6b80941b57b803e8b12f4 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)