diff --git a/source/DefaultEcs/System/ASystem.cs b/source/DefaultEcs/System/ASystem.cs
index d8969e67..2fbf1ea7 100644
--- a/source/DefaultEcs/System/ASystem.cs
+++ b/source/DefaultEcs/System/ASystem.cs
@@ -20,7 +20,7 @@ public abstract class ASystem<T> : ISystem<T>
         /// <param name="runner">The <see cref="SystemRunner{T}"/> used to process the update in parallel if not null.</param>
         protected ASystem(SystemRunner<T> runner)
         {
-            _runner = runner;
+            _runner = runner ?? SystemRunner<T>.Default;
         }
 
         /// <summary>
@@ -60,14 +60,7 @@ public void Update(T state)
         {
             PreUpdate(state);
 
-            if (_runner != null)
-            {
-                _runner.Update(state, this);
-            }
-            else
-            {
-                Update(state, 0, 0);
-            }
+            _runner.Update(state, this);
 
             PostUpdate(state);
         }
diff --git a/source/DefaultEcs/System/SystemRunner.cs b/source/DefaultEcs/System/SystemRunner.cs
index a4e6abf0..bca1ed12 100644
--- a/source/DefaultEcs/System/SystemRunner.cs
+++ b/source/DefaultEcs/System/SystemRunner.cs
@@ -15,6 +15,8 @@ public sealed class SystemRunner<T> : IDisposable
     {
         #region Fields
 
+        internal static readonly SystemRunner<T> Default = new SystemRunner<T>(1);
+
         private readonly CancellationTokenSource _disposeHandle;
         private readonly ManualResetEventSlim[] _startHandles;
         private readonly ManualResetEventSlim[] _endHandles;
@@ -81,7 +83,7 @@ internal void Update(T state, ASystem<T> system)
                 handle.Set();
             }
 
-            _currentSystem.Update(_currentState, _tasks.Length, _tasks.Length);
+            system.Update(state, _tasks.Length, _tasks.Length);
 
             foreach (ManualResetEventSlim handle in _endHandles)
             {