diff --git a/datafusion/core/src/physical_plan/join_utils.rs b/datafusion/core/src/physical_plan/join_utils.rs
index b690522e5c85..662cebcd5bbd 100644
--- a/datafusion/core/src/physical_plan/join_utils.rs
+++ b/datafusion/core/src/physical_plan/join_utils.rs
@@ -170,6 +170,7 @@ fn output_join_field(old_field: &Field, join_type: &JoinType, is_left: bool) ->
     };
 
     if force_nullable {
+        // Could cleanup after https://github.com/apache/arrow-rs/issues/1934
         Field::new(old_field.name(), old_field.data_type().clone(), true)
     } else {
         old_field.clone()