diff --git a/src/sagemaker/workflow/callback_step.py b/src/sagemaker/workflow/callback_step.py
index 2c0f0f6355..3517b62c1f 100644
--- a/src/sagemaker/workflow/callback_step.py
+++ b/src/sagemaker/workflow/callback_step.py
@@ -49,7 +49,7 @@ class CallbackOutput:
     """
 
     output_name: str = attr.ib(default=None)
-    output_type: CallbackOutputTypeEnum = attr.ib(default=CallbackOutputTypeEnum.String.value)
+    output_type: CallbackOutputTypeEnum = attr.ib(default=CallbackOutputTypeEnum.String)
 
     def to_request(self) -> RequestType:
         """Get the request structure for workflow service calls."""
diff --git a/tests/unit/sagemaker/workflow/test_callback_step.py b/tests/unit/sagemaker/workflow/test_callback_step.py
index e8161ac16b..d02b1cf7bf 100644
--- a/tests/unit/sagemaker/workflow/test_callback_step.py
+++ b/tests/unit/sagemaker/workflow/test_callback_step.py
@@ -53,6 +53,29 @@ def test_callback_step():
     }
 
 
+def test_callback_step_default_values():
+    param = ParameterInteger(name="MyInt")
+    outputParam1 = CallbackOutput(output_name="output1")
+    cb_step = CallbackStep(
+        name="MyCallbackStep",
+        depends_on=["TestStep"],
+        sqs_queue_url="https://sqs.us-east-2.amazonaws.com/123456789012/MyQueue",
+        inputs={"arg1": "foo", "arg2": 5, "arg3": param},
+        outputs=[outputParam1],
+    )
+    cb_step.add_depends_on(["SecondTestStep"])
+    assert cb_step.to_request() == {
+        "Name": "MyCallbackStep",
+        "Type": "Callback",
+        "DependsOn": ["TestStep", "SecondTestStep"],
+        "SqsQueueUrl": "https://sqs.us-east-2.amazonaws.com/123456789012/MyQueue",
+        "OutputParameters": [
+            {"OutputName": "output1", "OutputType": "String"},
+        ],
+        "Arguments": {"arg1": "foo", "arg2": 5, "arg3": param},
+    }
+
+
 def test_callback_step_output_expr():
     param = ParameterInteger(name="MyInt")
     outputParam1 = CallbackOutput(output_name="output1", output_type=CallbackOutputTypeEnum.String)