diff --git a/src/core/Elsa.Core/Activities/ControlFlow/Join/Join.cs b/src/core/Elsa.Core/Activities/ControlFlow/Join/Join.cs
index d6df8aa98..acb2fa67c 100644
--- a/src/core/Elsa.Core/Activities/ControlFlow/Join/Join.cs
+++ b/src/core/Elsa.Core/Activities/ControlFlow/Join/Join.cs
@@ -72,7 +72,7 @@ namespace Elsa.Activities.ControlFlow
             return Done();
         }
 
-        private async Task RecordInboundTransitionsAsync(ActivityExecutionContext activityExecutionContext, CancellationToken cancellationToken)
+        private void RecordInboundTransitionsAsync(ActivityExecutionContext activityExecutionContext)
         {
             var workflowExecutionContext = activityExecutionContext.WorkflowExecutionContext;
             var activityInstance = activityExecutionContext.ActivityInstance;
@@ -117,9 +117,10 @@ namespace Elsa.Activities.ControlFlow
             return $"@{sourceActivityId}_{sourceOutcomeName}";
         }
 
-        public async Task Handle(ActivityExecuted notification, CancellationToken cancellationToken)
+        public Task Handle(ActivityExecuted notification, CancellationToken cancellationToken)
         {
-            await RecordInboundTransitionsAsync(notification.ActivityExecutionContext, cancellationToken);
+            RecordInboundTransitionsAsync(notification.ActivityExecutionContext);
+            return Task.CompletedTask;
         }
     }
 }
\ No newline at end of file
diff --git a/src/core/Elsa.Core/Activities/Primitives/Correlate/SetVariableBuilderExtensions.cs b/src/core/Elsa.Core/Activities/Primitives/Correlate/SetVariableBuilderExtensions.cs
index 5038e4f99..77b427833 100644
--- a/src/core/Elsa.Core/Activities/Primitives/Correlate/SetVariableBuilderExtensions.cs
+++ b/src/core/Elsa.Core/Activities/Primitives/Correlate/SetVariableBuilderExtensions.cs
@@ -10,10 +10,10 @@ namespace Elsa.Activities.ControlFlow
     public static class CorrelateBuilderExtensions
     {
         public static IOutcomeBuilder Correlate(this IBuilder builder, Action<ISetupActivity<Correlate>> setup) => builder.Then(setup).When(OutcomeNames.Done);
-        public static IOutcomeBuilder Correlate(this IBuilder builder, Func<ActivityExecutionContext, ValueTask<string>> value) => builder.Correlate(activity => activity.Set(x => x.Value, value));
-        public static IOutcomeBuilder Correlate(this IBuilder builder, Func<ActivityExecutionContext, string> value) => builder.Correlate(activity => activity.Set(x => x.Value, value));
-        public static IOutcomeBuilder Correlate(this IBuilder builder, Func<ValueTask<string>> value) => builder.Correlate(activity => activity.Set(x => x.Value, value));
-        public static IOutcomeBuilder Correlate(this IBuilder builder, Func<string> value) => builder.Correlate(activity => activity.Set(x => x.Value, value));
-        public static IOutcomeBuilder Correlate(this IBuilder builder, string value) => builder.Correlate(activity => activity.Set(x => x.Value, value));
+        public static IOutcomeBuilder Correlate(this IBuilder builder, Func<ActivityExecutionContext, ValueTask<string?>> value) => builder.Correlate(activity => activity.Set(x => x.Value, value));
+        public static IOutcomeBuilder Correlate(this IBuilder builder, Func<ActivityExecutionContext, string?> value) => builder.Correlate(activity => activity.Set(x => x.Value, value));
+        public static IOutcomeBuilder Correlate(this IBuilder builder, Func<ValueTask<string?>> value) => builder.Correlate(activity => activity.Set(x => x.Value, value));
+        public static IOutcomeBuilder Correlate(this IBuilder builder, Func<string?> value) => builder.Correlate(activity => activity.Set(x => x.Value, value));
+        public static IOutcomeBuilder Correlate(this IBuilder builder, string? value) => builder.Correlate(activity => activity.Set(x => x.Value, value));
     }
 }
\ No newline at end of file
diff --git a/src/core/Elsa.Core/Builders/SetupActivity.cs b/src/core/Elsa.Core/Builders/SetupActivity.cs
index 76de16877..c2799f54d 100644
--- a/src/core/Elsa.Core/Builders/SetupActivity.cs
+++ b/src/core/Elsa.Core/Builders/SetupActivity.cs
@@ -13,7 +13,7 @@ namespace Elsa.Builders
         public IDictionary<string, Func<ActivityExecutionContext, ValueTask<object?>>> ValueProviders { get; } =
             new Dictionary<string, Func<ActivityExecutionContext, ValueTask<object?>>>();
 
-        public ISetupActivity<T> Set<TProperty>(Expression<Func<T, TProperty>> propertyAccessor,
+        public ISetupActivity<T> Set<TProperty>(Expression<Func<T, TProperty?>> propertyAccessor,
             Func<ActivityExecutionContext, ValueTask<TProperty?>> valueFactory)
         {
             var propertyInfo = propertyAccessor.GetProperty()!;
diff --git a/src/core/Elsa.Core/Services/WorkflowRunner.cs b/src/core/Elsa.Core/Services/WorkflowRunner.cs
index c63f3b04c..0dc789736 100644
--- a/src/core/Elsa.Core/Services/WorkflowRunner.cs
+++ b/src/core/Elsa.Core/Services/WorkflowRunner.cs
@@ -66,7 +66,7 @@ namespace Elsa.Services
                 if (result.WorkflowInstanceId != null)
                 {
                     var workflowInstance = await _workflowInstanceManager.GetByIdAsync(result.WorkflowInstanceId, cancellationToken);
-                    await RunWorkflowAsync(result.WorkflowBlueprint, workflowInstance, result.ActivityId, input, cancellationToken);
+                    await RunWorkflowAsync(result.WorkflowBlueprint, workflowInstance!, result.ActivityId, input, cancellationToken);
                 }
                 else
                     await RunWorkflowAsync(result.WorkflowBlueprint, result.ActivityId, input, correlationId, contextId, cancellationToken);