diff --git a/py-polars/polars/dataframe/frame.py b/py-polars/polars/dataframe/frame.py
index 9f0c9b39b8d5..9af5858ab8b4 100644
--- a/py-polars/polars/dataframe/frame.py
+++ b/py-polars/polars/dataframe/frame.py
@@ -6379,8 +6379,14 @@ def pivot(
         columns
             Name of the column(s) whose values will be used as the header of the output
             DataFrame.
-        aggregate_function : {'first', 'sum', 'max', 'min', 'mean', 'median', 'last', 'count'}
-            A predefined aggregate function str or an expression.
+        aggregate_function
+            Choose from:
+
+            - None: no aggregation takes place, will raise error if multiple values are in group.
+            - A predefined aggregate function string, one of
+              {'first', 'sum', 'max', 'min', 'mean', 'median', 'last', 'count'}
+            - An expression to do the aggregation.
+
         maintain_order
             Sort the grouped keys so that the output order is predictable.
         sort_columns