diff --git a/quantum/extensions/providernet.py b/quantum/extensions/providernet.py
index 1422fbad46..b37436c25f 100644
--- a/quantum/extensions/providernet.py
+++ b/quantum/extensions/providernet.py
@@ -18,19 +18,14 @@
 from quantum.api import extensions
 from quantum.api.v2 import attributes
 
-
 NETWORK_TYPE = 'provider:network_type'
 PHYSICAL_NETWORK = 'provider:physical_network'
 SEGMENTATION_ID = 'provider:segmentation_id'
 
-# TODO(salvatore-orlando): Devise a solution for allowing plugins
-# to alter the set of allowed values
-NETWORK_TYPE_VALUES = ['flat', 'gre', 'local', 'vlan', 'stt']
-
 EXTENDED_ATTRIBUTES_2_0 = {
     'networks': {
         NETWORK_TYPE: {'allow_post': True, 'allow_put': True,
-                       'validate': {'type:values': NETWORK_TYPE_VALUES},
+                       'validate': {'type:string': None},
                        'default': attributes.ATTR_NOT_SPECIFIED,
                        'is_visible': True},
         PHYSICAL_NETWORK: {'allow_post': True, 'allow_put': True,