diff --git a/DDG4/celeritas/Celeritas.cpp b/DDG4/celeritas/Celeritas.cpp
index 457894ac5..1134c79ed 100644
--- a/DDG4/celeritas/Celeritas.cpp
+++ b/DDG4/celeritas/Celeritas.cpp
@@ -20,7 +20,7 @@
 using namespace dd4hep::sim;
 
 // Global shared setup options
-celeritas::SetupOptions& CelerSetupOptions()
+celeritas::SetupOptions& dd4hep::sim::CelerSetupOptions()
 {
   static celeritas::SetupOptions options = [] {
     // Construct setup options the first time CelerSetupOptions is invoked
@@ -53,21 +53,21 @@ celeritas::SetupOptions& CelerSetupOptions()
 }
 
 // Shared data and GPU setup
-celeritas::SharedParams& CelerSharedParams()
+celeritas::SharedParams& dd4hep::sim::CelerSharedParams()
 {
   static celeritas::SharedParams sp;
   return sp;
 }
 
 // Thread-local transporter
-celeritas::LocalTransporter& CelerLocalTransporter()
+celeritas::LocalTransporter& dd4hep::sim::CelerLocalTransporter()
 {
   static G4ThreadLocal celeritas::LocalTransporter lt;
   return lt;
 }
 
 // Thread-local offload interface
-celeritas::SimpleOffload& CelerSimpleOffload()
+celeritas::SimpleOffload& dd4hep::sim::CelerSimpleOffload()
 {
   static G4ThreadLocal celeritas::SimpleOffload so;
   return so;
diff --git a/DDG4/celeritas/Celeritas.h b/DDG4/celeritas/Celeritas.h
index 97b8ddd68..fe4282e3e 100644
--- a/DDG4/celeritas/Celeritas.h
+++ b/DDG4/celeritas/Celeritas.h
@@ -11,6 +11,15 @@ namespace dd4hep  {
   /// Namespace for the Geant4 based simulation part of the AIDA detector description toolkit
   namespace sim  {
     
+    // Global shared setup options
+    celeritas::SetupOptions& CelerSetupOptions();
+    // Shared data and GPU setup
+    celeritas::SharedParams& CelerSharedParams();
+    // Thread-local transporter
+    celeritas::LocalTransporter& CelerLocalTransporter();
+    // Thread-local offload
+    celeritas::SimpleOffload& CelerSimpleOffload();
+
     class EMPhysicsConstructor final : public G4EmStandardPhysics
     {
     public:
@@ -34,13 +43,4 @@ namespace dd4hep  {
   } /* End namespace sim */  
 } /* End namespace dd4hep*/
 
-// Global shared setup options
-celeritas::SetupOptions& CelerSetupOptions();
-// Shared data and GPU setup
-celeritas::SharedParams& CelerSharedParams();
-// Thread-local transporter
-celeritas::LocalTransporter& CelerLocalTransporter();
-// Thread-local offload
-celeritas::SimpleOffload& CelerSimpleOffload();
-
 #endif