diff --git a/e-suite.API/eSuite.API/Controllers/WorkflowTemplateController.cs b/e-suite.API/eSuite.API/Controllers/WorkflowTemplateController.cs
index d1221a7..0c06e60 100644
--- a/e-suite.API/eSuite.API/Controllers/WorkflowTemplateController.cs
+++ b/e-suite.API/eSuite.API/Controllers/WorkflowTemplateController.cs
@@ -167,7 +167,7 @@ public class WorkflowTemplateController : ESuiteControllerBase
     [ProducesResponseType(StatusCodes.Status400BadRequest, Type = typeof(ProblemDetails))]
     [AccessKey(SecurityAccess.DeleteWorkflowTemplate)]
     public async Task<IActionResult> GetAllowedTaskMetadataList(
-        [FromQuery] string taskType,
+        [FromQuery] string? taskType,
         CancellationToken cancellationToken = default!
     )
     {
diff --git a/e-suite.Modules.WorkflowTemplatesManager/WorkflowTemplateManager.cs b/e-suite.Modules.WorkflowTemplatesManager/WorkflowTemplateManager.cs
index f66f88e..70384d9 100644
--- a/e-suite.Modules.WorkflowTemplatesManager/WorkflowTemplateManager.cs
+++ b/e-suite.Modules.WorkflowTemplatesManager/WorkflowTemplateManager.cs
@@ -170,7 +170,7 @@ public class WorkflowTemplateManager : IWorkflowTemplateManager
         return $"{genericName}<{formattedArgs}>";
     }
 
-    public Task<List<TaskMetadata>> GetAllowedTaskMetadataList(string taskType, CancellationToken cancellationToken)
+    public Task<List<TaskMetadata>> GetAllowedTaskMetadataList(string? taskType, CancellationToken cancellationToken)
     {
         var taskTypeAttribute = StageExtensions.GetTaskAttributeType(taskType);
 
diff --git a/e-suite.Workflow.Core/Extensions/StageExtensions.cs b/e-suite.Workflow.Core/Extensions/StageExtensions.cs
index 823a62f..cb4ec2d 100644
--- a/e-suite.Workflow.Core/Extensions/StageExtensions.cs
+++ b/e-suite.Workflow.Core/Extensions/StageExtensions.cs
@@ -32,10 +32,10 @@ public static class StageExtensions
                 StringComparer.OrdinalIgnoreCase
             );
 
-    public static Type GetTaskAttributeType(string taskType)
+    public static Type? GetTaskAttributeType(string taskType)
     {
-        if (taskType == null)
-            throw new ArgumentNullException(nameof(taskType));
+        if (string.IsNullOrWhiteSpace(taskType))
+            return null;
 
         var key = taskType.Trim();
 
@@ -51,7 +51,7 @@ public static class StageExtensions
     }
 
 
-    private static readonly ConcurrentDictionary<Type, IEnumerable<Type>> AllowedTasksCache = new();
+    private static readonly ConcurrentDictionary<string, IEnumerable<Type>> AllowedTasksCache = new();
 
     [System.Diagnostics.CodeAnalysis.SuppressMessage(
         "Style", "IDE0305:Collection initialization can be simplified",
@@ -61,9 +61,21 @@ public static class StageExtensions
         Justification = "parameter required for extension method definition")]
 
 
-    public static IEnumerable<Type> GetAllowedTaskTypes(Type attributeType)
+    public static IEnumerable<Type> GetAllowedTaskTypes(Type? attributeType)
     {
-        return AllowedTasksCache.GetOrAdd(attributeType, _ =>
+        if (attributeType == null)
+        {
+            return AllowedTasksCache.GetOrAdd("__NULL__", _ =>
+            {
+                var generalTasks = GetAllowedTaskTypes(typeof(GeneralTaskAttribute));
+                var approvalTasks = GetAllowedTaskTypes(typeof(ApprovalTaskAttribute));
+
+                return generalTasks.Concat(approvalTasks).ToArray();
+            });
+        }
+
+
+        return AllowedTasksCache.GetOrAdd(attributeType!.FullName!, _ =>
         {
             return AppDomain.CurrentDomain
                 .GetAssemblies()