Underscore and java interfaces

Dear all,why does the following code not compile with error: unbound placeholder parameter on val gigaSpace:GigaSpace = _ ;
(The val value will be injected through reflection by Spring IOC)
Best RegardsEdmondo
class CurveComputationEventHandlersFactory {  @Autowired  val partitionManager:PartitionManager=_;  @Autowired   val gottwareRuntimeConfiguration:GottwareRuntimeConfiguration=_;  @GigaSpaceContext  val gigaSpace:GigaSpace=_;
}