diff --git a/quantum/wsgi.py b/quantum/wsgi.py
index dfd1bd7404..678391033b 100644
--- a/quantum/wsgi.py
+++ b/quantum/wsgi.py
@@ -284,6 +284,7 @@ class XMLDictSerializer(DictSerializer):
 
     def _to_xml(self, root):
         """Convert the xml object to an xml string."""
+        # we use lxml here instead of xml.minidom for performance reasons
         return etree.tostring(root, encoding='UTF-8', xml_declaration=True)
 
 
diff --git a/setup.py b/setup.py
index 0bc8d6aaf0..f294a3e57c 100644
--- a/setup.py
+++ b/setup.py
@@ -50,8 +50,7 @@ requires = [
     'PasteDeploy',
     'Routes>=1.12.3',
     'eventlet>=0.9.12',
-    'lxml==2.3',
-    'pep8>=0.6.1',
+    'lxml',
     'python-gflags',
     'simplejson',
     'sqlalchemy',
diff --git a/tools/pip-requires b/tools/pip-requires
index f13ef0d37d..ac357fa72e 100644
--- a/tools/pip-requires
+++ b/tools/pip-requires
@@ -2,7 +2,7 @@ Paste
 PasteDeploy==1.5.0
 Routes>=1.12.3
 eventlet>=0.9.12
-lxml==2.3
+lxml
 mox==0.5.3
 python-gflags==1.3
 simplejson