diff --git a/library/monads/state/State.scala b/library/monads/state/State.scala
index d1604868819653dea6f104ad37bb12e806e1563a..01ad0da3de8e94c0d85b94464b999b6d8a0d3f9a 100644
--- a/library/monads/state/State.scala
+++ b/library/monads/state/State.scala
@@ -46,10 +46,6 @@ case class State[S, A](runState: S => (A, S)) {
   @inline
   def >:: (s: S) = eval(s)
 
-  /** Helpers */
-  @isabelle.noBody
-  def forever[B]: State[S, B] = this >> forever
-
   def apply(s: S) = runState(s)
 
 }