diff --git a/lib/spack/spack/architecture.py b/lib/spack/spack/architecture.py
index 14a8c567938..dac3a45b798 100644
--- a/lib/spack/spack/architecture.py
+++ b/lib/spack/spack/architecture.py
@@ -207,7 +207,7 @@ def __str__(self):
                 self.platform_os.name + "-" + self.target.name)
         
     def _cmp_key(self):
-        return (self.platform.name, self.platform_os.name, self.target.name)
+        return (self.platform, self.platform_os, self.target)
 
 
 def _helper_to_dict(arch_field_dict, arch_field_name,  *args):