diff --git a/src/sagemaker/serve/spec/inference_spec.py b/src/sagemaker/serve/spec/inference_spec.py
index 0397e84975..9026c95841 100644
--- a/src/sagemaker/serve/spec/inference_spec.py
+++ b/src/sagemaker/serve/spec/inference_spec.py
@@ -30,9 +30,11 @@ def invoke(self, input_object: object, model: object):
 
     def preprocess(self, input_data: object):
         """Custom pre-processing function"""
+        return input_data
 
     def postprocess(self, predictions: object):
         """Custom post-processing function"""
+        return predictions
 
     def prepare(self, *args, **kwargs):
         """Custom prepare function"""