diff --git a/DDG4/plugins/Geant4SDActions.cpp b/DDG4/plugins/Geant4SDActions.cpp
index fcb427b2f0d07bd0876dba85d0b1f6ad0b6ce166..2b76038daac58ee23d6813500cf15f18c31ee4ce 100644
--- a/DDG4/plugins/Geant4SDActions.cpp
+++ b/DDG4/plugins/Geant4SDActions.cpp
@@ -219,7 +219,7 @@ namespace DD4hep {
             << " Post (" <<std::setw(24) << step->GetPostStepPoint()->GetMomentum() << ") "
             << std::endl;
 
-        std::cout << out;
+        std::cout << out.str();
 
         return true;
       }