play framework file missing needed by Diff

Question

I get this error when trying to use the lift-json library with scala play: "The file could not be compiled. Error raised is : error while loading Diff, class file needed by Diff is missing. reference type Serializable of package scala refers to nonexisting symbol."

I added "- net.liftweb -> lift-json 2.9.0-1-2.4" in my dependencies.yml file. I'm not sure what's producing this error.

Answer 1

Do play dependencies --sync, and redo play netbeansify or play eclipsify.