diff --git a/src/libCom/timer/timerPrivate.h b/src/libCom/timer/timerPrivate.h
index 66141ee4a..cd6689ca3 100644
--- a/src/libCom/timer/timerPrivate.h
+++ b/src/libCom/timer/timerPrivate.h
@@ -120,6 +120,8 @@ private:
     friend class timerQueueActiveMgr;
 };
 
+class timerQueueActiveMgr;
+
 class timerQueueActive : public epicsTimerQueueActive, 
     public epicsThreadRunable, public epicsTimerQueueNotify,
     public timerQueueActiveMgrPrivate {