diff --git a/LightweightIocContainer/Interfaces/Registrations/IOpenGenericRegistration.cs b/LightweightIocContainer/Interfaces/Registrations/IOpenGenericRegistration.cs
index 2159675..8279731 100644
--- a/LightweightIocContainer/Interfaces/Registrations/IOpenGenericRegistration.cs
+++ b/LightweightIocContainer/Interfaces/Registrations/IOpenGenericRegistration.cs
@@ -9,5 +9,5 @@ namespace LightweightIocContainer.Interfaces.Registrations;
 /// </summary>
 public interface IOpenGenericRegistration : ITypedRegistration
 {
-        
+    internal Type CreateGenericImplementationType<T>();
 }
\ No newline at end of file
diff --git a/LightweightIocContainer/IocContainer.cs b/LightweightIocContainer/IocContainer.cs
index f31230a..8a9d370 100644
--- a/LightweightIocContainer/IocContainer.cs
+++ b/LightweightIocContainer/IocContainer.cs
@@ -235,10 +235,7 @@ public class IocContainer : IIocContainer, IIocResolver
         switch (result)
         {
             case true when registration is IOpenGenericRegistration openGenericRegistration:
-            {
-                Type genericImplementationType = openGenericRegistration.ImplementationType.MakeGenericType(typeof(T).GenericTypeArguments);
-                return (true, new InternalToBeResolvedPlaceholder(genericImplementationType, registration, parametersToResolve), null);
-            }
+                return (true, new InternalToBeResolvedPlaceholder(openGenericRegistration.CreateGenericImplementationType<T>(), registration, parametersToResolve), null);
             case true:
                 return (true, new InternalToBeResolvedPlaceholder(registeredType, registration, parametersToResolve), null);
         }
@@ -383,21 +380,16 @@ public class IocContainer : IIocContainer, IIocResolver
     /// <returns>A newly created instance of the given <see cref="Type"/></returns>
     private T CreateInstance<T>(IRegistration registration, object?[]? arguments)
     {
-        T instance;
-        if (registration is IOpenGenericRegistration openGenericRegistration)
+        T instance = registration switch
         {
-            //create generic implementation type from generic arguments of T
-            Type genericImplementationType = openGenericRegistration.ImplementationType.MakeGenericType(typeof(T).GenericTypeArguments);
-            instance = Creator.CreateInstance<T>(genericImplementationType, arguments);
-        }
-        else if (registration is ISingleTypeRegistration<T> singleTypeRegistration)
-            instance = singleTypeRegistration.FactoryMethod == null ? Creator.CreateInstance<T>(singleTypeRegistration.InterfaceType, arguments) : singleTypeRegistration.FactoryMethod(this);
-        else if (registration is ILifestyleProvider { Lifestyle: Lifestyle.Multiton } and IMultitonRegistration multitonRegistration)
-            instance = CreateMultitonInstance<T>(multitonRegistration, arguments);
-        else if (registration is ITypedRegistration defaultRegistration)
-            instance = Creator.CreateInstance<T>(defaultRegistration.ImplementationType, arguments);
-        else
-            throw new UnknownRegistrationException($"There is no registration of type {registration.GetType().Name}.");
+            IOpenGenericRegistration openGenericRegistration => Creator.CreateInstance<T>(openGenericRegistration.CreateGenericImplementationType<T>(), arguments),
+            ISingleTypeRegistration<T> singleTypeRegistration => singleTypeRegistration.FactoryMethod == null
+                ? Creator.CreateInstance<T>(singleTypeRegistration.InterfaceType, arguments)
+                : singleTypeRegistration.FactoryMethod(this),
+            ILifestyleProvider { Lifestyle: Lifestyle.Multiton } and IMultitonRegistration multitonRegistration => CreateMultitonInstance<T>(multitonRegistration, arguments),
+            ITypedRegistration defaultRegistration => Creator.CreateInstance<T>(defaultRegistration.ImplementationType, arguments),
+            _ => throw new UnknownRegistrationException($"There is no registration of type {registration.GetType().Name}.")
+        };
 
         if (registration is ILifestyleProvider { Lifestyle: Lifestyle.Singleton })
             _singletons.TryAdd(GetType<T>(registration), instance);
@@ -741,6 +733,7 @@ public class IocContainer : IIocContainer, IIocResolver
     private Type GetType<T>(IRegistration registration) =>
         registration switch
         {
+            IOpenGenericRegistration openGenericRegistration => openGenericRegistration.CreateGenericImplementationType<T>(),
             ITypedRegistration typedRegistration => typedRegistration.ImplementationType,
             ISingleTypeRegistration<T> singleTypeRegistration => singleTypeRegistration.InterfaceType,
             _ => throw new UnknownRegistrationException($"Unknown registration used: {registration.GetType().Name}.")
diff --git a/LightweightIocContainer/Registrations/OpenGenericRegistration.cs b/LightweightIocContainer/Registrations/OpenGenericRegistration.cs
index 37c85cb..fb95140 100644
--- a/LightweightIocContainer/Registrations/OpenGenericRegistration.cs
+++ b/LightweightIocContainer/Registrations/OpenGenericRegistration.cs
@@ -29,6 +29,8 @@ internal class OpenGenericRegistration : RegistrationBase, IOpenGenericRegistrat
     /// </summary>
     public Type ImplementationType { get; }
 
+    public Type CreateGenericImplementationType<T>() => ImplementationType.MakeGenericType(typeof(T).GenericTypeArguments);
+
     /// <summary>
     /// Validate this <see cref="OpenGenericRegistration"/>
     /// </summary>
diff --git a/Test.LightweightIocContainer/OpenGenericRegistrationTest.cs b/Test.LightweightIocContainer/OpenGenericRegistrationTest.cs
index 8f09b3e..8b09088 100644
--- a/Test.LightweightIocContainer/OpenGenericRegistrationTest.cs
+++ b/Test.LightweightIocContainer/OpenGenericRegistrationTest.cs
@@ -20,6 +20,9 @@ public class OpenGenericRegistrationTest
     
     [UsedImplicitly]
     public class Constraint : IConstraint;
+
+    [UsedImplicitly]
+    public class AnotherConstraint : IConstraint;
         
     [UsedImplicitly]
     [SuppressMessage("ReSharper", "UnusedTypeParameter")]
@@ -50,15 +53,27 @@ public class OpenGenericRegistrationTest
     }
 
     [UsedImplicitly]
-    public interface IA;
+    public interface IA
+    {
+        ITest<Constraint> Test { get; }
+    }
     
     [UsedImplicitly]
-    public class A : IA
+    public class A(ITest<Constraint> test) : IA
     {
-        public A(ITest<Constraint> test)
-        {
-            
-        }
+        public ITest<Constraint> Test { get; } = test;
+    }
+
+    [UsedImplicitly]
+    public interface IB
+    {
+        ITest<AnotherConstraint> Test { get; }
+    }
+    
+    [UsedImplicitly]
+    public class B(ITest<AnotherConstraint> test) : IB
+    {
+        public ITest<AnotherConstraint> Test { get; } = test;
     }
 
     [SetUp]
@@ -126,4 +141,20 @@ public class OpenGenericRegistrationTest
         IA a = _iocContainer.Resolve<IA>();
         Assert.That(a, Is.TypeOf<A>());
     }
+    
+    [Test]
+    public void TestOpenGenericTypeAsParameterDifferentGenericParametersResolveDifferentSingletons()
+    {
+        _iocContainer.Register(r => r.Add<IA, A>());
+        _iocContainer.Register(r => r.Add<IB, B>());
+        _iocContainer.Register(r => r.AddOpenGenerics(typeof(ITest<>), typeof(Test<>), Lifestyle.Singleton));
+        
+        IA a = _iocContainer.Resolve<IA>();
+        Assert.That(a, Is.TypeOf<A>());
+        
+        IB b = _iocContainer.Resolve<IB>();
+        Assert.That(b, Is.TypeOf<B>());
+        
+        Assert.That(b.Test, Is.Not.SameAs(a.Test));
+    }
 }
\ No newline at end of file