diff --git a/src/expr/core/src/window_function/state/buffer.rs b/src/expr/core/src/window_function/state/buffer.rs
index c2402933e613e..ba064042c0021 100644
--- a/src/expr/core/src/window_function/state/buffer.rs
+++ b/src/expr/core/src/window_function/state/buffer.rs
@@ -336,6 +336,7 @@ impl<K: Ord, V: Clone> WindowImpl for RowsWindow<K, V> {
     }
 }
 
+/// The sliding window implementation for `RANGE` frames.
 pub(super) struct RangeWindow<V: Clone> {
     frame_bounds: RangeFrameBounds,
     _phantom: std::marker::PhantomData<V>,