diff --git a/GaudiKernel/GaudiKernel/ConcurrencyFlags.h b/GaudiKernel/GaudiKernel/ConcurrencyFlags.h
index 4ffb1675e0b340411fc5560f72eb52f19a8cfbd5..667dd444ba07baafa1a45390b4403d95d66a403a 100644
--- a/GaudiKernel/GaudiKernel/ConcurrencyFlags.h
+++ b/GaudiKernel/GaudiKernel/ConcurrencyFlags.h
@@ -20,6 +20,11 @@ class AthMpEvtLoopMgr;
  *
  */
 
+namespace SG
+{
+  class HiveMgrSvc;
+}
+
 namespace Gaudi
 {
 
@@ -31,7 +36,7 @@ namespace Gaudi
 
       friend class ::ThreadPoolSvc;
       friend class ::HiveWhiteBoard;
-      friend class ::SGHiveMgrSvc;    // ATLAS
+      friend class SG::HiveMgrSvc;    // ATLAS
       friend class ::AthMpEvtLoopMgr; // ATLAS
 
     public: