diff --git a/src/modules/Elsa.Http/Extensions/OutputExtensions.cs b/src/modules/Elsa.Http/Extensions/OutputExtensions.cs
index 977fc9377..f4ae784e9 100644
--- a/src/modules/Elsa.Http/Extensions/OutputExtensions.cs
+++ b/src/modules/Elsa.Http/Extensions/OutputExtensions.cs
@@ -8,9 +8,9 @@ internal static class OutputExtensions
     /// <summary>
     /// Gets the target type of the specified variable type.
     /// </summary>
-    public static Type? GetTargetType(this Output output, ActivityExecutionContext context)
+    public static Type? GetTargetType(this Output? output, ActivityExecutionContext context)
     {
-        var memoryBlock = output.MemoryBlockReference() is Variable variable
+        var memoryBlock = output?.MemoryBlockReference() is Variable variable
             ? context.WorkflowExecutionContext.MemoryRegister.TryGetBlock(variable.Id, out var block)
                 ? block
                 : default