Play framework2.4 can not add key store value to .scala build sbt file

Question

I'am trying to upgrade to play framework 2.4 from play 2.3, but when refreshing SBT I got the following error:

build/*:resourceDirectory from build/*:privateKeystore ((project.Build).scala:10)
[error]      Did you mean build/compile:resourceDirectory

I'am using .scala file as SBT build file

play 2.3: which used to be working well

 privateKeystore := confDirectory.value / "myProject.private.jks"

play 2.4: the change that caused the error

 privateKeystore := resourceDirectory.value / "myProject.private.jks"

note that confDirectory is not found for play2.4