diff --git a/Modules/Core/Common/include/itkSingleton.h b/Modules/Core/Common/include/itkSingleton.h
index 3fe961648de..5f2ce22cca9 100644
--- a/Modules/Core/Common/include/itkSingleton.h
+++ b/Modules/Core/Common/include/itkSingleton.h
@@ -59,7 +59,7 @@ class ITKCommon_EXPORT SingletonIndex
   }
 
 
-  // returns true if the globalName has not been registered yet.
+  // Returns true.
   //
   // It is assumed that the global will remain valid until the start
   // of globals being destroyed.
@@ -70,7 +70,8 @@ class ITKCommon_EXPORT SingletonIndex
                     std::function<void(void *)> func,
                     std::function<void()>       deleteFunc)
   {
-    return this->SetGlobalInstancePrivate(globalName, global, func, deleteFunc);
+    this->SetGlobalInstancePrivate(globalName, global, func, deleteFunc);
+    return true;
   }
 
   /** Set/Get the pointer to GlobalSingleton.
@@ -90,9 +91,9 @@ class ITKCommon_EXPORT SingletonIndex
   // work, and could use some type of Holder<T> class for intrinsic types
   void *
   GetGlobalInstancePrivate(const char * globalName);
-  // If globalName is already registered than false is return,
-  // otherwise global is added to the singleton index under globalName
-  bool
+
+  // global is added or set to the singleton index under globalName
+  void
   SetGlobalInstancePrivate(const char *                globalName,
                            void *                      global,
                            std::function<void(void *)> func,
@@ -119,11 +120,7 @@ Singleton(const char * globalName, std::function<void(void *)> func, std::functi
   if (instance == nullptr)
   {
     instance = new T;
-    if (!SingletonIndex::GetInstance()->SetGlobalInstance<T>(globalName, instance, func, deleteFunc))
-    {
-      delete instance;
-      instance = nullptr;
-    }
+    SingletonIndex::GetInstance()->SetGlobalInstance<T>(globalName, instance, func, deleteFunc);
   }
   return instance;
 }
diff --git a/Modules/Core/Common/src/itkSingleton.cxx b/Modules/Core/Common/src/itkSingleton.cxx
index d76b1e88051..1607971baa1 100644
--- a/Modules/Core/Common/src/itkSingleton.cxx
+++ b/Modules/Core/Common/src/itkSingleton.cxx
@@ -96,17 +96,15 @@ SingletonIndex::GetGlobalInstancePrivate(const char * globalName)
   return std::get<0>(it->second);
 }
 
-// If globalName is already registered remove it from map,
+// If globalName is already registered, set its global as specified,
 // otherwise global is added to the singleton index under globalName
-bool
+void
 SingletonIndex::SetGlobalInstancePrivate(const char *                globalName,
                                          void *                      global,
                                          std::function<void(void *)> func,
                                          std::function<void()>       deleteFunc)
 {
-  m_GlobalObjects.erase(globalName);
-  m_GlobalObjects.insert(std::make_pair(globalName, std::make_tuple(global, func, deleteFunc)));
-  return true;
+  m_GlobalObjects.insert_or_assign(globalName, std::make_tuple(global, func, deleteFunc));
 }
 
 SingletonIndex *