diff --git a/Event/EventBookkeeperTools/src/CutFlowSvc.cxx b/Event/EventBookkeeperTools/src/CutFlowSvc.cxx
index 8c4a77b2c5378176d73d3a93599c6284c209239e..ed028ec3d97e2f78f72be8e4e952449b0ff1fe3d 100644
--- a/Event/EventBookkeeperTools/src/CutFlowSvc.cxx
+++ b/Event/EventBookkeeperTools/src/CutFlowSvc.cxx
@@ -129,7 +129,7 @@ CutFlowSvc::addEvent( CutIdentifier cutID, double weight)
 {
   ATH_MSG_INFO("Adding event with weight "<< weight << "to cut " << cutID);
 
-  std::lock_guard<std::recursive_mutex> lock();
+  std::lock_guard<std::recursive_mutex> lock(m_addEventMutex);
 
   xAOD::CutBookkeeper* cbk = getCutBookkeeper(cutID);
   if (cbk == nullptr) {