MissingMethodException: UnityEngine.Debug.DrowRay

Hello;
i got this error:

MissingMethodException: UnityEngine.Debug.DrowRay
Boo.Lang.Runtime.DynamicDispatching.MethodDispatcherFactory.ProduceExtensionDispatcher ()
Boo.Lang.Runtime.DynamicDispatching.MethodDispatcherFactory.Create ()
Boo.Lang.Runtime.RuntimeServices.DoCreateMethodDispatcher (System.Object target, System.Type targetType, System.String name, System.Object args)
Boo.Lang.Runtime.RuntimeServices.CreateMethodDispatcher (System.Object target, System.String name, System.Object args)
Boo.Lang.Runtime.RuntimeServices+c__AnonStorey15.<>m__9 ()
Boo.Lang.Runtime.DynamicDispatching.DispatcherCache.Get (Boo.Lang.Runtime.DynamicDispatching.DispatcherKey key, Boo.Lang.Runtime.DynamicDispatching.DispatcherFactory factory)
Boo.Lang.Runtime.RuntimeServices.GetDispatcher (System.Object target, System.String cacheKeyName, System.Type cacheKeyTypes, Boo.Lang.Runtime.DynamicDispatching.DispatcherFactory factory)
Boo.Lang.Runtime.RuntimeServices.GetDispatcher (System.Object target, System.Object args, System.String cacheKeyName, Boo.Lang.Runtime.DynamicDispatching.DispatcherFactory factory)
Boo.Lang.Runtime.RuntimeServices.Invoke (System.Object target, System.String name, System.Object args)
UnityScript.Lang.UnityRuntimeServices.Invoke (System.Object target, System.String name, System.Object args, System.Type scriptBaseType)
RayShoot.RayShoot () (at Assets/scripts/RayShoot.js:12)
RayShoot.Update () (at Assets/scripts/RayShoot.js:6)

Thanks.

DrawRay

Not DrowRay.