diff --git a/source/poodinis/container.d b/source/poodinis/container.d
index fd549e7..dbb6a81 100644
--- a/source/poodinis/container.d
+++ b/source/poodinis/container.d
@@ -13,7 +13,8 @@
 
 module poodinis.container;
 
-import poodinis.registration : Registration, singleInstance, toConcreteTypeListString;
+import poodinis.registration : Registration, singleInstance,
+    toConcreteTypeListString, initializeFactoryType;
 import poodinis.autowire : AutowiredRegistration, AutowireInstantiationContext;
 import poodinis.factory : ConstructorInjectingInstanceFactory;
 import poodinis.valueinjection : ValueInjectionException;
@@ -202,7 +203,7 @@ synchronized class DependencyContainer
         auto instanceFactory = new ConstructorInjectingInstanceFactory!ConcreteType(this);
         auto newRegistration = new AutowiredRegistration!ConcreteType(registeredType,
                 instanceFactory, this);
-        newRegistration.singleInstance();
+        newRegistration.initializeFactoryType().singleInstance();
 
         static if (!is(SuperType == ConcreteType))
         {
diff --git a/source/poodinis/registration.d b/source/poodinis/registration.d
index 36c8f72..8323510 100644
--- a/source/poodinis/registration.d
+++ b/source/poodinis/registration.d
@@ -95,6 +95,29 @@ class Registration
     }
 }
 
+private InstanceFactoryParameters copyFactoryParameters(Registration registration)
+{
+    return registration.instanceFactory.factoryParameters;
+}
+
+private void setFactoryParameters(Registration registration, InstanceFactoryParameters newParameters)
+{
+    registration.instanceFactory.factoryParameters = newParameters;
+}
+
+/**
+ * Sets the registration's instance factory type the same as the registration's.
+ *
+ * This is not a registration scope. Typically used by Poodinis internally only.
+ */
+public Registration initializeFactoryType(Registration registration)
+{
+    auto params = registration.copyFactoryParameters();
+    params.instanceType = registration.instanceType;
+    registration.setFactoryParameters(params);
+    return registration;
+}
+
 /**
  * Scopes registrations to return the same instance every time a given registration is resolved.
  *
@@ -102,8 +125,9 @@ class Registration
  */
 public Registration singleInstance(Registration registration)
 {
-    registration.instanceFactory.factoryParameters = InstanceFactoryParameters(
-            registration.instanceType, CreatesSingleton.yes);
+    auto params = registration.copyFactoryParameters();
+    params.createsSingleton = CreatesSingleton.yes;
+    registration.setFactoryParameters(params);
     return registration;
 }
 
@@ -112,8 +136,10 @@ public Registration singleInstance(Registration registration)
  */
 public Registration newInstance(Registration registration)
 {
-    registration.instanceFactory.factoryParameters = InstanceFactoryParameters(
-            registration.instanceType, CreatesSingleton.no);
+    auto params = registration.copyFactoryParameters();
+    params.createsSingleton = CreatesSingleton.no;
+    params.existingInstance = null;
+    registration.setFactoryParameters(params);
     return registration;
 }
 
@@ -122,22 +148,23 @@ public Registration newInstance(Registration registration)
  */
 public Registration existingInstance(Registration registration, Object instance)
 {
-    registration.instanceFactory.factoryParameters = InstanceFactoryParameters(
-            registration.instanceType, CreatesSingleton.yes, instance);
+    auto params = registration.copyFactoryParameters();
+    params.createsSingleton = CreatesSingleton.yes;
+    params.existingInstance = instance;
+    registration.setFactoryParameters(params);
     return registration;
 }
 
 /**
  * Scopes registrations to create new instances using the given initializer delegate.
  */
-public Registration initializedBy(T)(Registration registration, T delegate() initializer) 
-    if(is(T == class) || is(T == interface)) 
+public Registration initializedBy(T)(Registration registration, T delegate() initializer)
+        if (is(T == class) || is(T == interface))
 {
-    registration.instanceFactory.factoryParameters = InstanceFactoryParameters(
-            registration.instanceType, CreatesSingleton.no, null, {
-        return cast(Object) initializer();
-    });
-
+    auto params = registration.copyFactoryParameters();
+    params.createsSingleton = CreatesSingleton.no;
+    params.factoryMethod = () => cast(Object) initializer();
+    registration.setFactoryParameters(params);
     return registration;
 }
 
@@ -146,11 +173,10 @@ public Registration initializedBy(T)(Registration registration, T delegate() ini
  */
 public Registration initializedOnceBy(T : Object)(Registration registration, T delegate() initializer)
 {
-    registration.instanceFactory.factoryParameters = InstanceFactoryParameters(
-            registration.instanceType, CreatesSingleton.yes, null, {
-        return cast(Object) initializer();
-    });
-
+    auto params = registration.copyFactoryParameters();
+    params.createsSingleton = CreatesSingleton.yes;
+    params.factoryMethod = () => cast(Object) initializer();
+    registration.setFactoryParameters(params);
     return registration;
 }
 
diff --git a/test/poodinis/autowiretest.d b/test/poodinis/autowiretest.d
index ec2e070..a70253b 100644
--- a/test/poodinis/autowiretest.d
+++ b/test/poodinis/autowiretest.d
@@ -129,7 +129,7 @@ version (unittest)
         container.register!ComponentA;
 
         auto registration = new AutowiredRegistration!ComponentB(typeid(ComponentB),
-                new InstanceFactory(), container).singleInstance();
+                new InstanceFactory(), container).initializeFactoryType().singleInstance();
         auto instance = cast(ComponentB) registration.getInstance(
                 new AutowireInstantiationContext());
 
diff --git a/test/poodinis/registrationtest.d b/test/poodinis/registrationtest.d
index bf8f095..7bdec0a 100644
--- a/test/poodinis/registrationtest.d
+++ b/test/poodinis/registrationtest.d
@@ -24,7 +24,7 @@ version (unittest)
     unittest
     {
         Registration registration = new Registration(null, typeid(TestType),
-                new InstanceFactory(), null);
+                new InstanceFactory(), null).initializeFactoryType();
         auto chainedRegistration = registration.singleInstance();
         auto instance1 = registration.getInstance();
         auto instance2 = registration.getInstance();
@@ -38,7 +38,7 @@ version (unittest)
     unittest
     {
         Registration registration = new Registration(null, typeid(TestType),
-                new InstanceFactory(), null);
+                new InstanceFactory(), null).initializeFactoryType();
         auto chainedRegistration = registration.newInstance();
         auto instance1 = registration.getInstance();
         auto instance2 = registration.getInstance();
@@ -55,7 +55,7 @@ version (unittest)
         auto expectedInstance = new TestType();
         auto chainedRegistration = registration.existingInstance(expectedInstance);
         auto actualInstance = registration.getInstance();
-        assert(expectedInstance is expectedInstance,
+        assert(expectedInstance is actualInstance,
                 "Registration with existing instance scope did not return the same instance");
         assert(registration is chainedRegistration,
                 "Registration returned by scope setting is not the same as the registration being set");
@@ -65,10 +65,11 @@ version (unittest)
     unittest
     {
         Registration firstRegistration = new Registration(typeid(TestInterface),
-                typeid(TestImplementation), new InstanceFactory(), null).singleInstance();
+                typeid(TestImplementation), new InstanceFactory(), null).initializeFactoryType()
+            .singleInstance();
         Registration secondRegistration = new Registration(typeid(TestImplementation),
-                typeid(TestImplementation), new InstanceFactory(), null).singleInstance()
-            .linkTo(firstRegistration);
+                typeid(TestImplementation), new InstanceFactory(), null).initializeFactoryType()
+            .singleInstance().linkTo(firstRegistration);
 
         auto firstInstance = firstRegistration.getInstance();
         auto secondInstance = secondRegistration.getInstance();
@@ -76,4 +77,63 @@ version (unittest)
         assert(firstInstance is secondInstance);
     }
 
+    // Test custom factory method via initializedBy
+    unittest
+    {
+        Registration registration = new Registration(typeid(TestInterface),
+                typeid(TestImplementation), new InstanceFactory(), null);
+
+        registration.initializedBy({
+            auto instance = new TestImplementation();
+            instance.someContent = "createdbyinitializer";
+            return instance;
+        });
+
+        TestImplementation instanceOne = cast(TestImplementation) registration.getInstance();
+        TestImplementation instanceTwo = cast(TestImplementation) registration.getInstance();
+        assert(instanceOne.someContent == "createdbyinitializer");
+        assert(instanceTwo.someContent == "createdbyinitializer");
+        assert(instanceOne !is instanceTwo);
+    }
+
+    // Test custom factory method via initializedOnceBy
+    unittest
+    {
+        Registration registration = new Registration(typeid(TestInterface),
+                typeid(TestImplementation), new InstanceFactory(), null);
+
+        registration.initializedOnceBy({
+            auto instance = new TestImplementation();
+            instance.someContent = "createdbyinitializer";
+            return instance;
+        });
+
+        TestImplementation instanceOne = cast(TestImplementation) registration.getInstance();
+        TestImplementation instanceTwo = cast(TestImplementation) registration.getInstance();
+        assert(instanceOne.someContent == "createdbyinitializer");
+        assert(instanceTwo.someContent == "createdbyinitializer");
+        assert(instanceOne is instanceTwo);
+    }
+
+    // Test chaining single/new instance scope to initializedBy will not overwrite the factory method.
+    unittest
+    {
+        Registration registration = new Registration(typeid(TestInterface),
+                typeid(TestImplementation), new InstanceFactory(), null);
+
+        registration.initializedBy({
+            auto instance = new TestImplementation();
+            instance.someContent = "createdbyinitializer";
+            return instance;
+        });
+
+        registration.singleInstance();
+
+        TestImplementation instanceOne = cast(TestImplementation) registration.getInstance();
+        TestImplementation instanceTwo = cast(TestImplementation) registration.getInstance();
+        assert(instanceOne.someContent == "createdbyinitializer");
+        assert(instanceTwo.someContent == "createdbyinitializer");
+        assert(instanceOne is instanceTwo);
+    }
+
 }