diff --git a/py-polars/polars/dataframe/frame.py b/py-polars/polars/dataframe/frame.py
index 9545733410fc..21cddd52a81e 100644
--- a/py-polars/polars/dataframe/frame.py
+++ b/py-polars/polars/dataframe/frame.py
@@ -6940,7 +6940,8 @@ def join_asof(
         This is similar to a left-join except that we match on nearest key rather than
         equal keys.
 
-        Both DataFrames must be sorted by the asof_join key.
+        Both DataFrames must be sorted by the `on` key (within each `by` group, if
+        specified).
 
         For each row in the left DataFrame:
 
diff --git a/py-polars/polars/lazyframe/frame.py b/py-polars/polars/lazyframe/frame.py
index de33fe1bdcfc..14895dcd782e 100644
--- a/py-polars/polars/lazyframe/frame.py
+++ b/py-polars/polars/lazyframe/frame.py
@@ -4274,7 +4274,8 @@ def join_asof(
         This is similar to a left-join except that we match on nearest key rather than
         equal keys.
 
-        Both DataFrames must be sorted by the join_asof key.
+        Both DataFrames must be sorted by the `on` key (within each `by` group, if
+        specified).
 
         For each row in the left DataFrame: