have the same bug! Cannot use unity 17.3 :(

unity implement surface type shaders not for "flexibility"

it allow use standard lighting on all shaders, with-out change they self.

And i think it will be great, provide this opportunity for future, even if it will be have less flexibility

Forward or Deferred or Surface

they think too: https://www.assetstore.unity3d.com/en/#!/content/68570