diff --git a/src/Testing/CoreTests/Runtime/Handlers/HandlerGraphTests.cs b/src/Testing/CoreTests/Runtime/Handlers/HandlerGraphTests.cs
index a3de0368f..519d815f7 100644
--- a/src/Testing/CoreTests/Runtime/Handlers/HandlerGraphTests.cs
+++ b/src/Testing/CoreTests/Runtime/Handlers/HandlerGraphTests.cs
@@ -1,8 +1,12 @@
-using System.Diagnostics;
+using ImTools;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using Module1;
+using System.Diagnostics;
+using System.Reflection;
+using JasperFx.Core.Reflection;
 using Wolverine.Attributes;
+using Wolverine.Runtime;
 using Wolverine.Runtime.Handlers;
 using Wolverine.Util;
 using Xunit;
@@ -65,6 +69,25 @@ await Should.ThrowAsync<InvalidOperationException>(async () =>
                 }).StartAsync();
         });
     }
+
+    [Fact]
+    public async Task Concurrent_Registration_No_Race_Condition()
+    {
+        // just make sure the list consists of at least a couple of messages
+        var typesToRegister = typeof(DummyMessage).Assembly.GetTypes().Where(x => x.Name.EndsWith("Message")).ToArray();
+
+        using var host = await Host.CreateDefaultBuilder()
+            .UseWolverine()
+            .StartAsync();
+
+        var graph = host.Services.GetRequiredService<HandlerGraph>();
+        var runtime = host.Services.GetRequiredService<IWolverineRuntime>();
+        Parallel.ForEach(typesToRegister, t => runtime.RegisterMessageType(t));
+
+        var missingTypes = typesToRegister.Select(t => t.ToMessageTypeName())
+            .Where(t => graph.TryFindMessageType(t, out var _) is false).ToArray();
+        missingTypes.ShouldBeEmpty();
+    }
 }
 
 public class DummyMessage { }
diff --git a/src/Wolverine/Runtime/Handlers/HandlerGraph.cs b/src/Wolverine/Runtime/Handlers/HandlerGraph.cs
index ffda4a370..a9f926d90 100644
--- a/src/Wolverine/Runtime/Handlers/HandlerGraph.cs
+++ b/src/Wolverine/Runtime/Handlers/HandlerGraph.cs
@@ -46,6 +46,8 @@ public partial class HandlerGraph : ICodeFileCollectionWithServices, IWithFailur
 
     private bool _hasGrouped;
 
+    private object _messageTypesLock = new();
+
     private ImHashMap<string, Type> _messageTypes = ImHashMap<string, Type>.Empty;
 
     private ImmutableList<Type> _replyTypes = ImmutableList<Type>.Empty;
@@ -334,24 +336,28 @@ private void tryApplyLocalQueueConfiguration(WolverineOptions options)
 
     private void registerMessageTypes()
     {
-        _messageTypes =
-            _messageTypes.AddOrUpdate(typeof(Acknowledgement).ToMessageTypeName(), typeof(Acknowledgement));
-
-        foreach (var chain in Chains)
+        lock (_messageTypesLock)
         {
-            _messageTypes = _messageTypes.AddOrUpdate(chain.MessageType.ToMessageTypeName(), chain.MessageType);
+            _messageTypes =
+                _messageTypes.AddOrUpdate(typeof(Acknowledgement).ToMessageTypeName(), typeof(Acknowledgement));
 
-            if (chain.MessageType.TryGetAttribute<InteropMessageAttribute>(out var att))
+            foreach (var chain in Chains)
             {
-                _messageTypes = _messageTypes.AddOrUpdate(att.InteropType.ToMessageTypeName(), chain.MessageType);
-            }
-            else
-            {
-                foreach (var @interface in chain.MessageType.GetInterfaces())
+                _messageTypes = _messageTypes.AddOrUpdate(chain.MessageType.ToMessageTypeName(), chain.MessageType);
+
+                if (chain.MessageType.TryGetAttribute<InteropMessageAttribute>(out var att))
                 {
-                    if (InteropAssemblies.Contains(@interface.Assembly))
+                    _messageTypes = _messageTypes.AddOrUpdate(att.InteropType.ToMessageTypeName(), chain.MessageType);
+                }
+                else
+                {
+                    foreach (var @interface in chain.MessageType.GetInterfaces())
                     {
-                        _messageTypes = _messageTypes.AddOrUpdate(@interface.ToMessageTypeName(), chain.MessageType);
+                        if (InteropAssemblies.Contains(@interface.Assembly))
+                        {
+                            _messageTypes =
+                                _messageTypes.AddOrUpdate(@interface.ToMessageTypeName(), chain.MessageType);
+                        }
                     }
                 }
             }
@@ -465,8 +471,11 @@ public void RegisterMessageType(Type messageType)
             return;
         }
 
-        _messageTypes = _messageTypes.AddOrUpdate(messageType.ToMessageTypeName(), messageType);
-        _replyTypes = _replyTypes.Add(messageType);
+        lock (_messageTypesLock)
+        {
+            _messageTypes = _messageTypes.AddOrUpdate(messageType.ToMessageTypeName(), messageType);
+            _replyTypes = _replyTypes.Add(messageType);
+        }
     }
     
     public void RegisterMessageType(Type messageType, string messageAlias)
@@ -481,8 +490,11 @@ public void RegisterMessageType(Type messageType, string messageAlias)
             return;
         }
 
-        _messageTypes = _messageTypes.AddOrUpdate(messageAlias, messageType);
-        _replyTypes = _replyTypes.Add(messageType);
+        lock (_messageTypesLock)
+        {
+            _messageTypes = _messageTypes.AddOrUpdate(messageAlias, messageType);
+            _replyTypes = _replyTypes.Add(messageType);
+        }
     }
 
     public IEnumerable<HandlerChain> AllChains()