diff --git a/src/modules/Elsa.ProtoActor/Services/ProtoActorWorkflowRuntime.cs b/src/modules/Elsa.ProtoActor/Services/ProtoActorWorkflowRuntime.cs
index 3b3d04058..31c0b7bda 100644
--- a/src/modules/Elsa.ProtoActor/Services/ProtoActorWorkflowRuntime.cs
+++ b/src/modules/Elsa.ProtoActor/Services/ProtoActorWorkflowRuntime.cs
@@ -146,7 +146,7 @@ internal class ProtoActorWorkflowRuntime : IWorkflowRuntime
     }
 
     /// <inheritdoc />
-    public async Task<WorkflowExecutionResult> ResumeWorkflowAsync(string workflowInstanceId, ResumeWorkflowRuntimeOptions options, CancellationToken cancellationToken = default)
+    public async Task<WorkflowExecutionResult?> ResumeWorkflowAsync(string workflowInstanceId, ResumeWorkflowRuntimeOptions options, CancellationToken cancellationToken = default)
     {
         var request = new ResumeWorkflowRequest
         {
diff --git a/src/modules/Elsa.Workflows.Runtime/Contracts/IWorkflowRuntime.cs b/src/modules/Elsa.Workflows.Runtime/Contracts/IWorkflowRuntime.cs
index 9315f12bb..406d8d061 100644
--- a/src/modules/Elsa.Workflows.Runtime/Contracts/IWorkflowRuntime.cs
+++ b/src/modules/Elsa.Workflows.Runtime/Contracts/IWorkflowRuntime.cs
@@ -47,7 +47,7 @@ public interface IWorkflowRuntime
     /// <param name="workflowInstanceId">The ID of the workflow instance to resume.</param>
     /// <param name="options"></param>
     /// <param name="cancellationToken"></param>
-    Task<WorkflowExecutionResult> ResumeWorkflowAsync(string workflowInstanceId, ResumeWorkflowRuntimeOptions options, CancellationToken cancellationToken = default);
+    Task<WorkflowExecutionResult?> ResumeWorkflowAsync(string workflowInstanceId, ResumeWorkflowRuntimeOptions options, CancellationToken cancellationToken = default);
 
     /// <summary>
     /// Resumes all workflows that are bookmarked on the specified activity type. 
diff --git a/src/modules/Elsa.Workflows.Runtime/Services/DefaultWorkflowInbox.cs b/src/modules/Elsa.Workflows.Runtime/Services/DefaultWorkflowInbox.cs
index 4ddc2890f..3b7af0ff2 100644
--- a/src/modules/Elsa.Workflows.Runtime/Services/DefaultWorkflowInbox.cs
+++ b/src/modules/Elsa.Workflows.Runtime/Services/DefaultWorkflowInbox.cs
@@ -25,11 +25,11 @@ public class DefaultWorkflowInbox : IWorkflowInbox
     /// Initializes a new instance of the <see cref="DefaultWorkflowInbox"/> class.
     /// </summary>
     public DefaultWorkflowInbox(
-        IWorkflowRuntime workflowRuntime, 
-        IWorkflowInboxStore store, 
-        INotificationSender notificationSender, 
-        ISystemClock systemClock, 
-        IIdentityGenerator identityGenerator, 
+        IWorkflowRuntime workflowRuntime,
+        IWorkflowInboxStore store,
+        INotificationSender notificationSender,
+        ISystemClock systemClock,
+        IIdentityGenerator identityGenerator,
         IBookmarkHasher bookmarkHasher)
     {
         _workflowRuntime = workflowRuntime;
@@ -51,7 +51,7 @@ public class DefaultWorkflowInbox : IWorkflowInbox
     public async ValueTask<SubmitWorkflowInboxMessageResult> SubmitAsync(NewWorkflowInboxMessage newMessage, WorkflowInboxMessageDeliveryOptions options, CancellationToken cancellationToken = default)
     {
         var now = _systemClock.UtcNow;
-        
+
         // Create a new message.
         var message = new WorkflowInboxMessage
         {
@@ -66,22 +66,38 @@ public class DefaultWorkflowInbox : IWorkflowInbox
             Input = newMessage.Input,
             Hash = _bookmarkHasher.Hash(newMessage.ActivityTypeName, newMessage.BookmarkPayload),
         };
-        
+
         // Store the message.
         await _store.SaveAsync(message, cancellationToken);
-        
+
         // Send a notification.
         var strategy = options.EventPublishingStrategy;
         var workflowExecutionResults = new List<WorkflowExecutionResult>();
         var notification = new WorkflowInboxMessageReceived(message, workflowExecutionResults);
         await _notificationSender.SendAsync(notification, strategy, cancellationToken);
-        
+
         // Return the result.
         return new SubmitWorkflowInboxMessageResult(message, workflowExecutionResults);
     }
 
     /// <inheritdoc />
     public async ValueTask<DeliverWorkflowInboxMessageResult> DeliverAsync(WorkflowInboxMessage message, CancellationToken cancellationToken = default)
+    {
+        var triggeredWorkflows = await TriggerWorkflowsAsync(message, cancellationToken);
+
+        message.IsHandled = triggeredWorkflows.Any();
+
+        if (message.IsHandled)
+        {
+            message.AffectedWorkflowInstancesIds = triggeredWorkflows.Select(x => x.WorkflowInstanceId).ToList();
+            message.HandledAt = _systemClock.UtcNow;
+            await _store.SaveAsync(message, cancellationToken);
+        }
+
+        return new DeliverWorkflowInboxMessageResult(triggeredWorkflows);
+    }
+
+    private async Task<ICollection<WorkflowExecutionResult>> TriggerWorkflowsAsync(WorkflowInboxMessage message, CancellationToken cancellationToken = default)
     {
         var activityTypeName = message.ActivityTypeName;
         var correlationId = message.CorrelationId;
@@ -90,18 +106,12 @@ public class DefaultWorkflowInbox : IWorkflowInbox
         var bookmarkPayload = message.BookmarkPayload;
         var input = message.Input;
         var options = new TriggerWorkflowsRuntimeOptions(correlationId, workflowInstanceId, activityInstanceId, input);
-        var result = await _workflowRuntime.TriggerWorkflowsAsync(activityTypeName, bookmarkPayload, options, cancellationToken);
-        
-        message.IsHandled = result.TriggeredWorkflows.Any();
 
-        if (message.IsHandled)
-        {
-            message.AffectedWorkflowInstancesIds = result.TriggeredWorkflows.Select(x => x.WorkflowInstanceId).ToList();
-            message.HandledAt = _systemClock.UtcNow;
-            await _store.SaveAsync(message, cancellationToken);
-        }
-        
-        return new DeliverWorkflowInboxMessageResult(result.TriggeredWorkflows);
+        if (workflowInstanceId != null)
+            return await _workflowRuntime.ResumeWorkflowsAsync(activityTypeName, bookmarkPayload, options, cancellationToken);
+
+        var result = await _workflowRuntime.TriggerWorkflowsAsync(activityTypeName, bookmarkPayload, options, cancellationToken);
+        return result.TriggeredWorkflows;
     }
 
     /// <inheritdoc />
diff --git a/src/modules/Elsa.Workflows.Runtime/Services/DefaultWorkflowRuntime.cs b/src/modules/Elsa.Workflows.Runtime/Services/DefaultWorkflowRuntime.cs
index 6b6bcb8ab..d857d149f 100644
--- a/src/modules/Elsa.Workflows.Runtime/Services/DefaultWorkflowRuntime.cs
+++ b/src/modules/Elsa.Workflows.Runtime/Services/DefaultWorkflowRuntime.cs
@@ -119,14 +119,14 @@ public class DefaultWorkflowRuntime : IWorkflowRuntime
     }
 
     /// <inheritdoc />
-    public async Task<WorkflowExecutionResult> ResumeWorkflowAsync(string workflowInstanceId, ResumeWorkflowRuntimeOptions options, CancellationToken cancellationToken = default)
+    public async Task<WorkflowExecutionResult?> ResumeWorkflowAsync(string workflowInstanceId, ResumeWorkflowRuntimeOptions options, CancellationToken cancellationToken = default)
     {
         await using (await _distributedLockProvider.AcquireLockAsync(workflowInstanceId, TimeSpan.FromMinutes(1), cancellationToken))
         {
             var workflowState = await _workflowStateStore.FindAsync(workflowInstanceId, cancellationToken);
 
             if (workflowState == null)
-                throw new Exception($"Workflow instance {workflowInstanceId} not found");
+                return null;
 
             var definitionId = workflowState.DefinitionId;
             var version = workflowState.DefinitionVersion;
@@ -309,7 +309,8 @@ public class DefaultWorkflowRuntime : IWorkflowRuntime
                 },
                 cancellationToken);
 
-            resumedWorkflows.Add(new WorkflowExecutionResult(workflowInstanceId, resumeResult.Status, resumeResult.SubStatus, resumeResult.Bookmarks));
+            if (resumeResult != null)
+                resumedWorkflows.Add(new WorkflowExecutionResult(workflowInstanceId, resumeResult.Status, resumeResult.SubStatus, resumeResult.Bookmarks));
         }
 
         return resumedWorkflows;