diff --git a/src/crewai/task.py b/src/crewai/task.py
index 7f12bebab..748e401e4 100644
--- a/src/crewai/task.py
+++ b/src/crewai/task.py
@@ -19,6 +19,8 @@ from typing import (
     Tuple,
     Type,
     Union,
+    get_args,
+    get_origin,
 )
 
 from pydantic import (
@@ -183,7 +185,6 @@ class Task(BaseModel):
             # Check return annotation if present, but don't require it
             return_annotation = sig.return_annotation
             if return_annotation != inspect.Signature.empty:
-                from typing import get_args, get_origin
 
                 return_annotation_args = get_args(return_annotation)
                 if not (
@@ -194,6 +195,7 @@ class Task(BaseModel):
                         return_annotation_args[1] is Any
                         or return_annotation_args[1] is str
                         or return_annotation_args[1] is TaskOutput
+                        or return_annotation_args[1] == Union[str, TaskOutput]
                     )
                 ):
                     raise ValueError(
diff --git a/tests/task_test.py b/tests/task_test.py
index eed69859c..ac25a14f8 100644
--- a/tests/task_test.py
+++ b/tests/task_test.py
@@ -4,6 +4,7 @@ import hashlib
 import json
 import os
 from functools import partial
+from typing import Tuple, Union
 from unittest.mock import MagicMock, patch
 
 import pytest
@@ -241,11 +242,11 @@ def test_guardrail_type_error():
             return (True, x)
 
         @classmethod
-        def guardrail_class_fn(cls, x: TaskOutput) -> tuple[bool, TaskOutput]:
+        def guardrail_class_fn(cls, x: TaskOutput) -> tuple[bool, str]:
             return (True, x)
 
         @staticmethod
-        def guardrail_static_fn(x: TaskOutput) -> tuple[bool, TaskOutput]:
+        def guardrail_static_fn(x: TaskOutput) -> tuple[bool, Union[str, TaskOutput]]:
             return (True, x)
 
     obj = Object()
@@ -268,7 +269,7 @@ def test_guardrail_type_error():
         guardrail=Object.guardrail_static_fn,
     )
 
-    def error_fn(x: TaskOutput, y: bool) -> tuple[bool, TaskOutput]:
+    def error_fn(x: TaskOutput, y: bool) -> Tuple[bool, TaskOutput]:
         return (y, x)
 
     Task(