diff --git a/src/libCom/fdmgr/fdmgr.cpp b/src/libCom/fdmgr/fdmgr.cpp
index 131c6e9a3..5748acd19 100644
--- a/src/libCom/fdmgr/fdmgr.cpp
+++ b/src/libCom/fdmgr/fdmgr.cpp
@@ -62,6 +62,8 @@ private:
 	epicsShareFunc virtual void callBack ();
 };
 
+class oldFdmgr;
+
 //
 // osiTimerForOldFdmgr
 //