In my build.sbt file included the line:

libraryDependencies += "javax.servlet" % "servlet-api" % "2.5" % "provided"

When I compiled the servlet api jar was not on the classpath. I removed the % "provided" and the project compiled correctly. I don't know if this is a general problem IE if scala has the problem or if it is only a problem with javac. Or perhaps the way to define scopes has changed in 0.9.1. I assumed it was the same since there are so many similarities between 0.91 and 0.7.x.