diff --git a/scene/3d/node_3d.h b/scene/3d/node_3d.h
index 90c7bc89efd..04f73a4cbdd 100644
--- a/scene/3d/node_3d.h
+++ b/scene/3d/node_3d.h
@@ -96,6 +96,7 @@ private:
 
 	mutable SelfList<Node> xform_change;
 
+	// This Data struct is to avoid namespace pollution in derived classes.
 	struct Data {
 		mutable Transform3D global_transform;
 		mutable Transform3D local_transform;
diff --git a/scene/gui/control.h b/scene/gui/control.h
index 7e997ef3d51..e526690cbe7 100644
--- a/scene/gui/control.h
+++ b/scene/gui/control.h
@@ -159,6 +159,7 @@ private:
 		}
 	};
 
+	// This Data struct is to avoid namespace pollution in derived classes.
 	struct Data {
 		// Global relations.
 
diff --git a/scene/main/node.h b/scene/main/node.h
index 4e6530cccd3..8c82c41e46d 100644
--- a/scene/main/node.h
+++ b/scene/main/node.h
@@ -91,6 +91,7 @@ private:
 		SceneTree::Group *group = nullptr;
 	};
 
+	// This Data struct is to avoid namespace pollution in derived classes.
 	struct Data {
 		String scene_file_path;
 		Ref<SceneState> instance_state;