diff --git a/bigframes/functions/_function_session.py b/bigframes/functions/_function_session.py
index 6d2f0dbd57..7fb5cc114b 100644
--- a/bigframes/functions/_function_session.py
+++ b/bigframes/functions/_function_session.py
@@ -740,9 +740,12 @@ def udf(
         BigQuery managed function.
 
         .. note::
-            The udf must be self-contained, i.e. it must not contain any
+            This feature is in preview. The code in the udf must be
+            (1) self-contained, i.e. it must not contain any
             references to an import or variable defined outside the function
-            body.
+            body, and
+            (2) Python 3.11 compatible, as that is the environment
+            in which the code is executed in the cloud.
 
         .. note::
             Please have following IAM roles enabled for you:
@@ -801,7 +804,7 @@ def udf(
                 https://pip.pypa.io/en/stable/reference/requirements-file-format/.
         """
 
-        warnings.warn("udf is in preview.", category=bfe.PreviewWarning)
+        warnings.warn("udf is in preview.", category=bfe.PreviewWarning, stacklevel=5)
 
         # Some defaults may be used from the session if not provided otherwise.
         session = self._resolve_session(session)
diff --git a/bigframes/session/__init__.py b/bigframes/session/__init__.py
index 7229a4641b..b189c0e194 100644
--- a/bigframes/session/__init__.py
+++ b/bigframes/session/__init__.py
@@ -1426,9 +1426,12 @@ def udf(
         [BigQuery managed user-defined function](https://cloud.google.com/bigquery/docs/user-defined-functions-python).
 
         .. note::
-            The udf must be self-contained, i.e. it must not contain any
+            This feature is in preview. The code in the udf must be
+            (1) self-contained, i.e. it must not contain any
             references to an import or variable defined outside the function
-            body.
+            body, and
+            (2) Python 3.11 compatible, as that is the environment
+            in which the code is executed in the cloud.
 
         .. note::
             Please have BigQuery Data Editor (roles/bigquery.dataEditor) IAM